For "American Idol," it looks like so far, there really is life after Simon Cowell.

The top-rated show on TV entered its 10th season with many question marks: Would the ratings erosion of the last few years keep getting worse? After an underwhelming ninth season, and patchy groups of finalists in the years previous, was there enough undiscovered singing talent left to fuel the show? Would the star power of new judges Jennifer Lopez and Steven Tyler translate on a show that had made its own stars, and where previous big-name judge Ellen DeGeneres flamed out badly? And most of all, did the show work without Simon as the resident truth-teller?

And as the show prepares for the finals to begin tonight at 8 on FOX, things are looking surprisingly good, even though I still have some reservations about Tyler and J-Lo.

The ratings are down much less dramatically than feared - about 7% in the advertiser-coveted 18-49 year-old demographic - and on some nights, like last week's results show that announced the 13 finalists, the numbers have actually been up over last year.

Those 13 finalists - particularly the 5 men voted through by the audience - seems at first glance to be the deepest and most diverse group the show has had since at least season 7 (the David vs. David match-up that first let contestants play instruments). There's no obvious frontrunner yet - which is probably good for all involved, since the early favorite hasn't won since Carrie Underwood back in season 4 - but there are a bunch of singers who could very plausibly win this thing based on what little we've seen of them so far.

(Fienberg interviewed each member of the top 13 a few hours after they were chosen last week.)

One of the tweaks made by returning producer Nigel Lythgoe was to get rid of the guest mentors - record executive Jimmy Iovine will be the new in-house mentor - and make the theme weeks more elastic so that, for instance, a rock singer doesn't have to risk going home in Disco Night. (Tonight's theme involves the contestants picking songs by their favorite artists.) That's good news for a contestant like Scotty McCreery, a 17-year-old country singer who sounds eerily like Randy Travis, but who could easily struggle if nudged out of his comfort zone. Of course, some of the most memorable "Idol" performances of all time - good and bad - have come from singers having to work outside their chosen genre, while the "pick whatever kind of song you want" theme weeks are often the dullest, so I'm not convinced this is a good move for the show, even if it helps some of the singers.

In fact, easy as it was to bash Lythgoe when he was running "Idol" in its peak years for the show's various missteps, nearly every move he's made since returning has been the right one, particularly spending more time on the expanded Hollywood round (which often gives us the best sense of who these people are), and paring the semi-final round down to only a single week, so that we're not sick of the contestants by the time the finals begin. (On the other hand, that may be the main reason this year's finalists seem so relatively impressive. If Scotty, or twitchy singer-songwriter type Paul McDonald, or balladeer Pia Toscano had given three full performances by now, they might run the risk of seeming like one-trick ponies, just as so many initially impressive contestants did under the old format.)

As of now, the contestant side of things - easily the more important part of the show - seems in healthy shape, and the new judging panel has worked out much better than expected. And oddly, Tyler and Lopez have wound up splitting and then improving on the good qualities Paula Abdul once brought to the show.

Tyler is loopy and unpredictable, while still seeming much saner than Pauler ever did. The Aerosmith frontman seems genuinely happy to be here, where Ellen looked scared most of the time and Kara Dio Guardi was defensive of her place. As a bigger star than any of the contestants will likely ever be, Tyler's at ease with himself and his position on the show, and the good time he's having has been infectious for the other two judges.

Lopez, meanwhile, has taken Abdul's role as the nurturer on the panel. She really, really wants to see all these kids succeed, and seems hurt when they struggle. (When early favorite Chris Medina - a promising singer who was taking care of his brain-damaged fiancee - didn't make the cut for the semi-finals, Lopez acted more upset about it than he did.) She also seems very happy to be here - as well she should be, since this has been a great career move for her. Her new single, whose video aired on last week's results show, wound up at number 1 on the iTunes chart. And separated from all those horrible romantic comedies she made in the last decade, it's like the entire male demographic that watches "Idol" has had a collective, "Oh, yeah: J-Lo's gorgeous" reaction. She could squander all the goodwill by making "The Back-Up Plan 2: The Quickening," but so far, "Idol" has been very good to Jenny from the block.

And as the last dawg standing - and the one sitting in Simon's old spot at the judges' table - Randy Jackson has been forced out of his own comfort zone of pointless blather and catchphrases. He's become, shockingly, the most honest and useful judge up there. Again and again during the semi-finals, Tyler and J-Lo gave high praise to a mediocre performance, only for Randy to be the one to point out what was wrong with it. He doesn't have Simon's flair for creatively structuring his negative comments (most of his complaints last week revolved around contestants not changing their performances up enough from the original version), but at least he has a role now - and one that feels karmically appropriate, after all the years he led the studio audience in booing Simon for being the only honest guy up there.

Of course, the fact that the two newbies were so relentlessly effusive in their praise is a concern. They'll occasionally be negative, either if the singer is just blatantly terrible or if Randy is negative first, but outside of those two circumstances, they love every contestant and every performance. Tyler's so reluctant to actually, you know, judge that when Ryan Seacrest asked him on Thursday's show whether the men or women were better - about the most innocuous question possible given this gig - he said he couldn't choose. Even Paula managed to be critical now and then, even if she first had to couch it in some kind of compliment. ("You look so pretty up there, but...")

So there could be a problem down the road if what the judges say has little connection to what we're hearing at home, and/or if Randy grows sick of playing bad cop every week and reverts back to his bag of stupid catchphrases. And all the diversity of the finalists could go out the window if we wind up with another innocuous white guy with a guitar as our winner. (We're perilously close to the point where the show might need to have separate winners by gender to ensure a woman can win something.)

But at the moment, things have gone much, much better than most of us could have expected. "Idol" is relatively healthy, and if things continue this way, Simon's "X Factor" show is going to have a lot more pressure on it when it debuts in the fall. Everyone assumed that Simon made "Idol" work in America, but what if it was the other way around?

Alan Sepinwall may be reached at sepinwall@hitfix.com