Read below for my take on it.... may be minor spoilers in there (though I'm sure you can pretty much guess most of it anyway :)
First of all I was happy for Oneiros that Galactus was not represented by a guy in a robe. The trailer has a scene that indicates that the Surfer is talking to a hooded, robed guy who you assume is Galactus, but lucky for the comic book purists he's represented in a far bigger way.
The movie picks up a few months or years after the first movie, with the FF dealing with the ups and down of being superstars. They are drawn from their "normal" superhero lifestyle when a mysterious force in the form of the Silver Surfer appears, and they discover that the surfer precedes the complete destruction of any world that he visits.
The movie was fun, and in my opinion worth the $8 to see it in the theaters. There's definitely something about certain movies that, for me anyway, makes it worth going to the theater for the 'big screen' experience (of course, these days that involves over priced popcorn, 20 minutes of ads before the previews even start, people kicking the back of your chair, checking their cell phones, and spilling their drinks on your feet... not that I'm bitter!).
The special effects are great of course, and the characters are not bad. I still find Jessica Alba wooden and while incredibly attractive, somehow not sexy at all. She really tries hard to act in the wedding scene, but really (to me) seems to blend into the background. The Human Torch and The Thing were the main focus in this movie. There was a fairly good mix of comedy and seriousness, with the standard array of predictable characters coming in and out (the stern and unforgiving general, the evil guy who double crosses, etc). The action and storyline are probably very predictable for comic book fans (who know who/what Galactus and the Silver Surfer are and do) and only mostly predictable for most savvy movie goers.
Other than the predictability and wooden performance from a couple of the characters, the only real complaint I have about this movie (for what it is anyway) is there is a chase scene through some mountains with what I think were great special effects, but the chase happened at night, so you couldn't see the great effects!
My recommendation (as I don't have a proper rating system here) is go see it on cheap night at the theater, or go see it on DVD at a friends place with a nice 42" LCD TV and surround sound system ;)