When Joss Whedon took the job as director of "The Avengers," he had a specific challenge to overcome. Even after the success of the individual movies featuring Iron Man, Thor, and Captain America, it seemed like a nearly impossible task, juggling so many giant personalities in one coherent story.

Now the challenge is very different for him as writer/director, because he's following up one of the biggest films of all time, and he's also laying groundwork for the entire next phase of movies in the Marvel Cinematic Universe. The last time a director found himself in a similar position with Marvel was Jon Favreau on "Iron Man 2," and it's interesting to see the ways Whedon has responded differently, and the ways in which he's fallen into some of the same traps. Make no mistake… "Avengers: Age Of Ultron" is both a better film and a better sequel than "Iron Man 2," but I think it's clear at this point that as long as Marvel continues to build one large interlocked continuity, there are certain stumbling blocks that they will continue to face with the movies.

There is a ton of material to enjoy in "Age Of Ultron" for fans of each of the characters to enjoy, and for the first time, it feels like everything, from the heroes to the villains to the plotting, all serves a single theme. On that level, "Age Of Ultron" is a fairly impressive piece of work. Whedon has managed to bring all of these characters to a crisis point at the same time, and then set them up against a nearly impossible threat, and it's obvious that what he wants most is to see what happens to the Avengers after they've been pushed to this particular breaking point. And the action in the film is, honestly, some of the most direct-from-the-comics comic-book action ever captured on film. In the moments where it all comes together, like the sure-to-be-iconic Hulkbuster sequence, this is the very model of what Marvel's been chasing since day one.

While I enjoyed "Iron Man 3," its existence makes much of Tony Stark's journey in this film feel like a stutter. At the start of this film, Tony is still preoccupied with creating suits that can do the job of Iron Man without the man inside. The problem is that none of the robots are truly capable of thought or judgment, so they can't be the permanent solution that Tony is searching for.

The film opens as in-media-res as possible, with the Avengers launching an attack against the castle where Baron Von Strucker (Thomas Kretschmann) has been developing new HYDRA weapons and conducting the biological experiments we saw hinted at in the final moments of "Captain America: The Winter Soldier." What's fun about the way Whedon handles the Avengers in the action sequences now is that he makes sure to come up with new ways to play with their powers, both individually and as a team. It's not just punch, punch, punch, and there are some big laugh-out-loud gags.

Once they run into Wanda (Elizabeth Olsen) and Pietro (Aaron Taylor-Johnson), though, they find themselves tested in a whole new way. Wanda has the power to reach into people's minds and bring out the fears she finds there, making them seem real. She is a bad trip, and when she reaches into Tony Stark's mind, what she finds there is this yawning fear that he's still dealing with, caused when the sky above New York opened and an alien army spilled out. He got a glimpse at the other side of that hole in the sky, and he's afraid of what happens next time. He feels like it was luck that saved the day, and he is determined to remove chance from the equation.

I don't want to start to pull the story apart until you have a chance to see the film, so you can expect an in-depth post-release piece, like we've done with some of these films in the past. There's an entire character I am reluctant to discuss. Right now, there's still a lot of press that hasn't even had a chance to see the movie, and it's going to start rolling out in overseas theaters starting tomorrow, so spoilers will be everywhere. Just not here.

Instead, I'll say that the things that work best for me in this film are the human moments. There's a knock-out scene between Natasha (Scarlett Johansson) and Bruce (Mark Ruffalo) in the middle of the film that's just a conversation, but it's one of the most electric moments in the film. It could only come now, this far into the series, because we've had time with these people, and we've got a sense of history that can be played with. It feels like Whedon decided to go overboard making it up to Jeremy Renner for writing him as a mind-controlled zombie for most of the first film, and the result is one of the best character arcs in the film. Hawkeye emerges as a fully-formed personality this time, and he's enormously enjoyable. I expect fans will be vocal about him and about everything that happens between Natasha and Bruce, and that there will be phone-books full of fan fiction picking up the threads that are laid out in the film.

Whedon's use of Wanda and Pietro is also interesting. I think he gets the most value out of each of them that he can, and he writes them as characters first, not as good guys or bad guys. They are self-interested, certainly, but who isn't? That's ultimately the question facing each of these characters… what is more important? Their own personal agendas or the agenda of the Avengers? And can those two things always co-exist? Pretty much every terrible thing that happens in the film happens because someone tries to do something good, and in one of Whedon's nicest moves as a writer, when someone tries to do something very, very bad, it leads to perhaps one the most dramatic acts of good in the entire Marvel movie saga so far.

By the end of the film, things do not look the same for anyone in the film, and that certainly leaves a number of potential threads to be explored. But to some extent, it makes this feel like the middle of something. Yes, the Ultron story is told from start to finish here, and I think it features some really interesting ideas that will continue to resonate through the rest of these movies, but for most of the other characters, this is transition more than anything else. There's one character's fate that can be inferred from certain dialogue clues and from one shot in particular that should inspire spirited debate for a while, and that can be fun. But too much of that simply makes this feel like a very big episode of a TV show.

When I say "very big," by the way, I mean, "big on a scale that few films would attempt." This is a movie that is almost exhaustingly large-scale, and Ultron's ultimate plan involves a crazy visual idea that Whedon makes sort of beautiful and eerie. It's got so much action that I'm going to bet some audiences go numb after a while. But in scene after scene, there are beats and stunts and poses that suggest that an army of comic book fanatics worked on this movie, and as someone who has been reading comics for roughly forty years now, I find it kind of amazing that we have come to this point, where we're seeing things like this on a movie screen, and this is mainstream entertainment. This is this summer's biggest movie, and it is as weird as anything Marvel's made so far when you look at it with any sort of remove.

Anyone who enjoyed "Avengers" is going to be mightily entertained by "Avengers: Age Of Ultron," and hardcore fans are going to be able to spend the next year trying to pull this apart for clues, but as a film, it feels like it is constantly just on the verge of getting away from the filmmakers. While there's no post-credits scene, stay for the mid-credits sting that tells you exactly what the drive is going to be between this film and the next time the Avengers come together. If this one feels like it was hard to manage, that one should be positively massive as both challenge and, if successful, payoff.

And based on this one, I can see why Whedon tapped out.

"Avengers: Age of Ultron" opens in US theaters on May 1st.

A respected critic and commentator for fifteen years, Drew McWeeny helped create the online film community as "Moriarty" at Ain't It Cool News, and now proudly leads two budding Film Nerds in their ongoing movie education.