I saw this last night on blu-ray; I'd missed it in the cinema (the first one I didn't see on the big screen sadly) and this was my first rental in some time. Loved it. The scene in Dubai especially was brilliant, as was the climactic fight in the car factory. Great plot twists, clever use of technology (it served the plot, rather than vice-versa) and some nice humour. Great support from Renner and Pegg in particular and the cast in general. Oh and a couple of welcome cameos at the end, both of which came as a total surprise to me.
I've always thought that the series got progressively better - II was better than MI and III was better still. Not sure if I prefer this movie to III or not. Great and all as my new 46" widescreen HD tv is, it's not quite as good as the cinema, which is probably why I'm still tending towards III (plus III had a better villain). But I'll be sure to catch V in the cinema!