Second viewings are about 3 things: 
-seeing a movie for what it is rather than what you'd hoped it would be
-watching for details (visual or storytelling) you missed the first time around
-the internal consistency check:  does this story hold water when you know where it's going.  For that matter, does it get better when you know where it's going?

My second viewing of Transformers earlier this week passed all three counts with flying colors.  I did, in fact, enjoy Michael Bay's game of Rock 'Em Sock 'Em Robots a lot more the second time around for all three reasons.

-Transformers is, as I've mentioned in my original review, quite broad.  Broader, really, than any action movie should be.  But once the shock of that wares off, a second viewing shows that it's no Godzilla:  Bernie Mac's one scene is kinda nasty, and the endless, horrible scene where the Autobots try to “hide” outside Sam's house while his parents skulk around was even worse once I'd already seen it (OK, I liked the moment when the parents are overjoyed to see that their loser son is hiding a beautiful girl in his room, but that's a long way to go for a mild laugh).  In fact, I got up and went to the restroom during that sequence, came back and it still seemed to drone on for another ten minutes.  Yikes!  But on the plus side, John Turturo and Anthony Anderson seemed much more consistently in character than they'd seemed the first time around, even if Agent Simmons' underwear embarrass the filmmakers at least as much as they do him.

Another 2nd viewing advantage was being able to be patient with the movie's pace.  The first 90 minutes seemed awfully draggy to me the first time around, but I think a lot of that had to do with anxiety that Bay was never going to get around to delivering the goods.  Knowing that the climax is as goods-packed as can be, I was able to sit back and enjoy the deliberate build-up.

-There's so much visual business going on with the Autobots and Decepticons that one could just hit freeze-frame on the big screen and look them over all day.  I'm sure I'll be noticing new details on their amazing frames the 20th time I see the movie.

As a newcomer to the Transformers universe, it was also nice to have been able to touch base in the media with all the different in-jokes and reference to Transformers lore the movie contains and then notice them in their proper places.

-Another 2nd viewing benefit for a Transformers newbie such as myself was another chance to take stock of all the different Autobots and Decepticons in play, and to better understand the logistics of the climactic Royal Rumble.  In terms of motivation and strategy, it holds together very well, with the one exception that the Decepticons seem to give up a few good shots at Sam to turn and fight Autobot pursuers.  But I guess they're all really pissed at each other.

Anyway, to summarize, I had an even better time soaking up Transformers' pleasures in a nearly empty mid-week screening than I did in a packed house on its' opening night.  And I can't wait for the Autobots to roll out in the inevitable sequel in a couple years.