Disclaimer: I've not read but a couple F4 comics, and only seen a handful of animated TV episodes (the origin story in that one was pretty sad!), so if you're a loyalist YMMV.
I did thoroughly enjoy their treatment of the blue-eyed, ever-lovin' Thing.
The plot is simple, but not unreasonable. It's slightly more than two hours, and it's not all action-packed - there are some nice character moments. There's a considerable amount of friction among the team members, for example, almost to the point of being overdone. But seeing as how this is the team formation, and there's a lot of adjustment going on, you'd expect some friction, wouldn't you?
Johnny provides much of the humor, being a cocky, fun-loving flyboy, and that's also a significant percentage of the aforementioned friction. Victor I found kind of dull for most of the movie, but the endgame when he becomes Dr. Doom is pretty enjoyable. There's the obligitory cameo by Stan Lee, of course.
The movie is not without flaws. You've picked up on some already, I'm sure. There's a not-quite top-notch feel about it, though "adequate" is too bland a term. I don't know if they were saving money, or time, or what, but I'll give it a solid B+.
