Some more reactions from around the blogosphere as well as TV-land...
E! Entertainment Online has the ratings info:
The introduction of Cosmic Boy and other Legion of Superheroes members helped lead CW's Smallville (4.3 million) to its biggest audience since early November, the network said. The show also did its anti-Gossip Girl thing, and won the 8 p.m. hour in men 18-34.
The LA Times blog Hero Complex had an interview with Geoff Johns the day that the show aired.
JP: And about the "Legion" episode tonight?
GJ: Well, we introduce Cosmic Boy, Lightning Lad and Saturn Girl. Three founding members of the Legion.
JP: Any other characters that you may have wanted to add?
GJ: Well, we kind of introduce another one, but you'll have to watch and see. Legion fans will definitely get it.
TV Squad has a list full of in-jokes and references, most of which I got.
Screenrant calls it a "huge letdown".
Let’s cut to the chase - they were awful.
Now I get it - maybe in the comic books this is how “Lightning Lad” (Calum Worthy) acts, but to have someone as a member of something called the “Legion of Superheroes” who acts like a 12 year old twit was frankly, beyond annoying and just plain stupid. You’d think that 1,000 years in the future teenagers with such responsibility would be more mature.
On the other hand, Geekshow calls it "The single best episode of Smallville ever constructed".
The Legion of Superheroes took a visit to Smallville tonight in an episode written by comic scribe Geoff Johns. It was, without a doubt, the BEST episode of the entire series to date. Geoff Johns succeeded where every writer to ever work on the show has failed… he wrote the perfect episode of Smallville.
iFMagazine gave it a "B".
I liked the allusions to Clark’s future in this episode. Listening to Lightning Lad’s (Calum Worthy) criticisms of Clark lacking his cape or not being able to fly was just plain funny. Hearing Clark being called the Man of Steel or Davis being acknowledged as Doomsday for the first time was entertaining as well. As has been the theme for most of this season, SMALLVILLE is slowly catching up with Superman.
A recap from Beesite:
The trio that went back in time were perfect for taking down Braniac. They were kind of goofy though with Rokk reminding me of Mack from Always Sunny and Garth being a straight up dork. I am curious about what Lana is planning on doing and hope that her character stays on the show for a while.
Newsarama has the post-game wrap-up:
Was I the only one who viewed the trio of Cosmic Boy, Saturn Girl and Lightning Lad as a sort of superhero version of Harry Potter, Ron and Hermoine? Certainly reminded me of them.
...My take on the Legionnaires? The telepathic Imra, Saturn Girl, was nice to look at, but seemed off at times, a tad distant and removed when communicating telepathically. Rokk, Cosmic Boy, displayed intelligence and good leadership skills at times on top of his power over magnetism. I just thought at least with the hair that he looked like a 1991 throwback, like someone you'd see at a Gin Blossoms show, or the movie Singles. Garth, Lightning Lad, definitely brought energy to the trio, not surprising considering his electrical powers. Way more geeky than I'd even envisioned LL, but still fun to follow. His fascination in Superman mementos, like Clark's letterman jacket (found at the "Levitz Museum," natch), was endearing.
io9 says that the future looks familiar:
...How did the Legion of Super-Heroes (and writer Geoff Johns) hold up in their series debut?
The honest answer would be an uncertain "Pretty well, maybe?" While Johns' script was perfectly fine, it was also more of a regular Smallville effort than what comic fans have come to expect from Johns. Yes, there were the geek-friendly shout outs (A Legion of Substitute Heroes reference? Really?). But the scale was smaller and the formula much more generic than fans of his Green Lantern or even his Action Comics runs would've expected.
Here are the Television Without Pity recap and forum discussion of the episode, the Zap2It recap, and the CW Source recap.
You can also watch the episode online (for as long as this lasts) at MegaVideo and TV Dome.