To follow up:
I think Amanda Waller was well written and followed her characterization in comics very well. Pam Grier’s performance just didn’t do it for me. I would have also liked to see a larger actress play her.
Likewise, I thought the tension between Hawkman and Green Arrow was also very “in character” even if they couldn’t fit all the comic history between the two characters in this already busy episode. I agree that the actor playing Hawkman was okay in the quieter moments but he was so over the top for me in the action moments that I dreaded any scene he was in. Also, Hawkman isn’t one of my favorite characters in comics anyway so my bias probably played into my opinion of his major role in this mini-movie.
I can’t think of anything I really liked about the performance of the actor who played Icicle. Just cheesy and over the top. No subtlety. I like subtlety. 
As for Icicle taking out three JSA’ers all by himself, I can see him taking out the Wesley Dodds Sandman without much problem. Depending on the circumstances, I can see him taking out the Jack Knight Starman. I think my problem comes from the actual fight between Starman and Icicle being so short. It was like Starman didn’t even give him a good fight. I guess I’d say that the Starman take down was more unsatisfying than unbelievable. My biggest problem is with the Dr. Fate take down. Along with the Legion of Super-Heroes in an issue of Adventure Comics Digest, Dr. Fate was one of the first comic book characters I ever read and has been one of my favorites (depending on the incarnation) ever since. He’s a powerful character and, again, there was hardly any battle. Green Arrow was able to “save” Stargirl with his arrows, but Dr. Fate goes without a fight? Unsatisfying at best and I’m sticking with unbelievable on this one. I think Chance’s point (in his review on the front page) about the low budget and Pretender’s comments about the limits of so many characters in a two hour mini-movie “event” had a lot to do with this.
Did they ever reveal who was filming all of the JSA’ers in the flashback? If they did, I never caught it. I understand it’s a plot device, but I just kept thinking that they didn’t have handheld cameras “back in the day” and the footage looked as if that’s how it was recorded.
Having said that, it was fun to see all the characters referenced and I look forward to seeing some of the ones that haven’t yet made an appearance.
I don’t love Clark’s “costume” but it doesn’t turn me off. Martian Manhunter’s, whether he’s trapped in his human form or not, turns me off. Different strokes… 
Looking forward to more of Checkmate.
Really liked the point Stargirl made about the JSA being a family and seeing Green Arrow show up at the end and wanting to hang out. This season has been a lot about the tension between the Smallville “team” and it was nice to see some warmth between them again.
Of this seasons guest appearances (Legion, Wonder Twins, JSA), this was the least satisfying for me probably due to their being so many characters and such little time. I look forward to seeing more of the JSA in the future, but hopefully with fewer characters at a time.