We saw F4:2 today. It was pretty good; definitely better than the first one. There were some problems with it, such as the hand-waving explanations like "wherever the surfer goes, 8 days later the planet dies." Sandy was annoyed with how much advertising was in the movie. It also suffered from clichéd characters, like the general who's going to do things "his way," and thinks that he can do it without the superheroes.
I can't fault it too much if these are all that I can complain about, and the rest of the movie overshadowed the bad parts. They had some fun scenes, like when the Thing was playing with some fans in the airport. I'm especially glad that they avoided spending much time on the team infighting, even though it always seemed to be just around the corner. The movie had a heart; all the characters liked each other, and they were teaming up to solve the bigger problem. They seemed a lot more likable than the first film.
The special effects were pretty good, never seeming to get in the way or draw attention to themselves. The Silver Surfer was very well done, and was cool to watch and listen to. They wisely didn't go with the standard comic Galactus appearance, which I always thought was pretty lame and completely lacking in power. The movie's Galactus is much more menacing; it seems like a real threat, not some 100' giant with a ridiculous hat.
After seeing the first movie, I would not have expected them to make a sequel, nor would I have wanted to see it. But this was very watchable. It might not life changing, but I could watch it again.
Fantastic 4: Rise of the Silver Surfer: 4/5