Acting-wise, it's okay. Natalie Portman seems a little stiff at times, maybe coz I've been so used to see her in intense roles. Ashton Kutcher - no doubt, carries the whole story kind of nicely. I think the problem with rom-coms these days is that they try to make things funny. Dialogue, script, everything relies heavily on funny moments. The thing is, they try too hard and it shows. Less romantic moments - the ones that are there seem kind of forced, and as a result it doesn't have enough oomph.
The only funny moment is the carrot you-said-no-flowers thing. A nice weekend date movie, but not worth watching twice.