The first time I watched M:I-GP, I saw it in the theatre, in IMAX, and it pretty much blew my socks off (seriously, it was really loud - but I also really really enjoyed it). I enjoyed it so much that I just bought the Blu-ray.
I thought it held up really really well, and even though there were complaints that the IMAX sequences weren't expanded to a 16:9 aspect ratio, it still looked fucking ridiculous.
And even though I laughed more at how ridiculous it is, and the ridiculous product placement, I still really enjoyed it, and do not regret buying it. It's just really overall a ridiculous movie, in a good way I think. I also liked the making-of special features of shooting on the Burj and of the final parking garage sequence. I find that knowing more about how stunts are performed and how effects are created increases my enjoyment of a movie like this.
One question though - do all of the Mission: Impossible credits sequences show the entire movie? I thought it was a really weird approach, if not.