Grindhouse was a treat, and once again, a movie that fulfills its promises. If you go in expecting high cinema, you deserve to be disappointed. If you go in expecting awesome with a side dish of zombies and explosions, then you will be justly rewarded. The running time was a bit long, IMHO, so be warned. I think the fact that it's over three hours. The fake trailers were fantastic, and I totally want to see Machete. Also, the soundtrack is already on my shopping list. As are Rose McGowan and Zoe Bell.
Now, the spoilery section: I really think the second story suffered in its pacing. We had already sat through one movie, and the flow was just totally off. It was well worth the payoff, don't get me wrong. Just get to the point sooner, s'il vous plait.
The first one was pretty much perfect. And I love the missing reel gag.