Holiday-themed episodes have a tendency to play to nostalgia and tradition. They can be a cringe-inducing subset of the "every special episode" syndrome. The trick is to subvert the typical expectations that come with the territory. Buffy the Vampire Slayer, for example, managed to do it very well.
This particular spin on the convention is broken into three parts, where the coming together at a family meal brings more than just the usual level of conflict and recrimination. The treatment of each Thanksgiving dinner is more or less a success, and has everything to do with the strengths of the characters involved.
The best material belongs to Samuel and his carnival family, as the truth about Joseph Sullivan's death comes out. Suddenly Edgar's displeasure with Samuel from the beginning comes into focus. Hiro finally gets to show a bit of backbone, even if he's still mostly whining about Charlie, and one can only hope that this will lead to a permanent transition into a more serious character as a whole. (Especially since it is highly unlikely that we will ever see Charlie again.)
I still like Samuel, even if his motivations are now almost entirely villainous. Robert Knepper continues to give the character a sense of style and energy that has been missing from most of the cast for quite some time. Only Sylar seems to be given the same opportunity to stretch, and that had to be a concession to Zachery Quinto, to ensure that he remains on the show to the bitter end.
Speaking of Sylar, the Petrelli Thanksgiving dinner was a close second to the carnival festivities. While the carnival plot thread began to answer some lingering questions about Sullivan brothers, this plot thread took on the consequences of the third season finale. The emergence of Sylar brought on some deliciously evil moments, and I wasn't entirely sure that Angela was going to survive the night.
It occurred to me, however, that the writers managed to sneak some muddled storytelling into the mix. When Peter needed to follow Nathan in the previous episode, he absorbed Nathan's ability. But "Nathan" is really Sylar, programmed to believe that he can only use Nathan's flying ability. The core ability is still Sylar's innate ability to take on the abilities of others. So shouldn't Peter have absorbed Sylar's ability?
Of course, that would put Peter back on a level that is too high for the good of the plot, and would prevent the logical solution to the Sylar problem: getting everyone together at the carnival for one big Heroe smackdown. I still firmly believe that Sylar is going to return to the carnival, learn the secret of Samuel's power, and absorb it. If anyone can learn how to decouple Samuel's earth-moving power from the metahuman-cascade effect, Sylar could. And then the question would be: how do all those heroes fight Sylar, when just being around him suddenly gives him a massive power boost? (On the other hand, it could be the one thing that keeps Sylar in check, because he would have to stop killing everyone for powers to preserve his new power source.)
At any rate, this leaves only the Bennett family dinner, and as usual, that is far less effective than the other two plot threads. Those stories had Samuel and Sylar; this has Claire and the same Noah that has been grasping for a purpose this season. The antics with Sandra, Lauren, and Doug did provide a lighter counterpoint to the darker elements in the other plot threads, but it just underscored how little these characters have been measuring up.
I will say, however, that the return of Lauren was a nice touch, and the return of Gretchen was a pleasant surprise. The writers are doing a nice job of treading a fine line with Claire and Gretchen. While they are technically not together as a romantic couple, there are clear undertones of chemistry between them. I suspect the writers will keep riding that line, so that the viewers can draw their own conclusions, but this is less exploitive than it could have been.
The biggest problem with the episode is that it didn't move the plot forward overly much. This season has been all about the measured pace, but this brought the momentum down a notch. Nathan and Sylar could have had their final showdown already, and Claire didn't really need more time to decide that she was going to find Samuel. Hopefully this is simply the prelude to a more active next episode.