Part of it, I think, is because they rushed the script to beat the writer's strike back in 2007. But, yeah, it wasn't good.
I just watched it on DVD a couple weeks ago and it was the first time I'd seen it since opening night in the theater. It doesn't hold up. I have a lot of problems with it and really don't believe it should have been that hard to come up with a better idea for, well, just about everything.
And the sinking ice still pisses me off. That final battle was pretty terrible, as was some of the CGI during the Paris chase.