Emma Watson was an absolutely horrendous actress in the first and second movies. Man, in that first one, it was horrible. I think she's gotten progressively better though, and now (in my personal rankings of actors) she sits tightly at "mediocre".
Ron's gonna get Hermione, though. It's just too obvious.
JKR's said that there's gonna be a bit more romance in Halfblood Prince, so I think it'll set up the foundation of who he's gonna be with at least. And I'm pretty sure it's gonna be Cho.