My thought on this thing is that they should've done it as two hour-long movies. You can get the illusion of a cheezy double-feature without making people actually sit through 3+ hours of it just to get your joke across.
I can't find it online anywhere, but last month I read a review of Grindhouse that took both Tarantino and Rodriguez to task for not living up to their potential. To paraphrase the review, for the last ten years or so they've both been making movies for ten year old boys--themselves. I like 'em both, but they haven't impressed me for quite a long time.
I have to agree with shootER. I enjoyed 'Kill Bill' (part one much moreso than part two, though) and I liked 'Once Upon a Time in Mexico.' But, let's face it, these movies are--at best--masterpieces of style, not of substance. Tarantino is stuck in homage-cycle and Rodriguez has now fully explored and mastered the depiction of gunfights and associated action sequences. I wish Tarantino would surprise me again like he did with Pulp Fiction. Or at least revert to serviceable crime dramas like Reservoir Dogs or Jackie Brown. The endless homage theme is getting kinda old, no matter how well it's executed. I'll probably enjoy Grindhouse when I get around to seeing it, but I doubt it will be a GREAT movie.