I was a little worried when this episode started. First, there was Dean singing and doing MTV moves to "The Heat Of The Moment," which is the most OOC thing I've seen him do since the impromptu inside-the-Impala singing. I was embarrassed to watch both scenes, and (*cringe*) THIS OOC-Dean came back over and over during the episode.
All of the over-the-top moments in the first "round" of the Tuesday also had me worried. They were so excessively broad, as in "Hey, dumbass viewer-- you'll want to notice this for later!" Seriously, the vast majority of us aren't that stupid, and I hate being pandered to like that. Plus the obvious stealing from "Groundhog Day."
But... then there was the heartbreak of Dean getting shot (poor Sammy). And then the repeat of Tuesday, where Sam wisely decided not to go back to the Mystery Spot at night and then AUGH! Car! Oh Dean. :(
The way Sam got progressively more strung-out looking with each successive Tuesday kept the angst going even as the deaths became almost humorous (black humor). I foresaw the "choking at breakfast" and "piano (desk?) from above" coming, but not the shower (!) or the electrocution or the "Do these burritos taste funny to you?" (which made me LOL, and then feel like a sicko).
I very much liked the return of the Trickster, which settled out the issue of the corny similarities to a movie most of us have seen and why exactly the repeating day was possible.
And then, there was the MEGA-angst.
The destruction of Sam from within was fantastically shown-- the bleakness of his life without Dean (ow, ow, ow), the way he turned away from the comfort his friends could have given him, the growth of the dark pragmatism in him when all love and hope were gone. It hurt to watch, but I was very pleased with how well it was done.
Sam's pleading with the Trickster was heartbreaking. And then to have Dean back... thank you, Kripke, for that hug, and for Dean having enough understanding that he didn't pull away because even though it was just one day for him he knew it has to have been far too long for Sam.
I liked that Dean noticed Sam's distress at the end, though I honestly wish Sam had told him how bad the first version of that Wednesday had been. I'm betting there were still some sniffles and tears in the car after the relief of waking up to having Dean alive again.
And one of the best parts of the ending was that sense of fear in the way Sam looked around the motel room where everything he'd been so scared of had actually come to pass, at least inside his head. *sigh*
ETA: I forgot the horror of Sam's self-triage. What with "No Country For Old Men" and the "House, M.D." episode with the doctor doing all her own tests at the South Pole, I've already seen all the self-triage I can handle for the next ten years. Gah!