Take two of the sexiest Hollywood stars of the past few years, add some FX to a genre which never uses them, and then borrow some elements from "Planes, Trains and Automobiles", and you'll have this watchable piece of entertainment fluff which plays better as a romantic road movie than a comedy.
In fact the few laughs in the film come more from people embarassing themselves (either giving those puppy-dog love speeches or singing off-key) than anything else, the kind of humour you cringe at while watching. Nevertheless there's a few chuckles now and then ranging from a well-orchestrated strip dance in a gay bar to various couples commenting on the disappointments of marriage. Still, there's nowhere near enough laughs to really call this a comedy.
On the romance side it fares a bit better, though its main fault is not setting up the relationship between Ben and his fiancee (Tierney) more - so when Bullock comes on the scene were immediately rooting for her and Ben to get together rather than being pulled between the two. Despite what some critics say, Affleck and Bullock do have a nice on-screen chemistry - nothing hot, rather a low sizzle that works well. Bullock's role seems made for her - the free-minded spirit who enjoys life, and she plays it well.
Pity the role is dragged down a bit by various complications from the past which just seem to arise out of nowhere. Still, fans of Miss Bullock will be delighted by her performance which is most certainly watchable. Affleck finally gets to show off some of his range in a leading role. His previous lead ("Chasing Amy") was more believable, but he had almost the same expression throughout the flick. Here he gets to vary between all sorts of emotions, and when the waterworks (ie. tears) start flowing he's quite convincing.
Now as for the storyline, it rather seems like a number of sequences have been put together to create it and a few scenes really push the levels of unbelievability in terms of what's going on. Various continuity flaws pop up, while the film's underlying theme of "don't get into marriage unless your absolutely sure its with some you love" is practically flogged to death, the preachiness is just yawn-inducing.
Still, the unconventional aspects (incl. the much debated ending) are actually what keep it from being completely forgettable. The directing is slick, but the amount of really close closeups of Ben and Sandra is quite staggering (I now know how many moles and scars each of them has on their faces) which is a bit confining in movies but will play well on TV. All in all it really depends on if your a fan of the two leads. I am so I liked it.