The movie, that is, not the book.
For those that are only familiar with one and not the other - if you've only seen the movie; read the book and it's a lot better, but the movie will now seem shit. If you've only read the book; don't watch the movie.
The Eragon movie had big shoes to fill. Christopher Paolini (the author) has reaped in massive numbers of readers, and for good reason; it's a pretty decent book. And there's two more (and one on the way very soon) to follow.
But for some reason, despite the big interest in Eragon, the moviemakers thought that the Eragon movie wouldn't actually get that much interest. And so we have book inconsistencies, left right and centre. Sections in the book that take up long amounts of time may only find bare moments in the movie; in particular, one bit I remember - what was a large trading city in the book was reduced to some ramshackle dwellings on stilts in the water. Some great characters only barely mentioned. Argh! As well as that, there were bits - particularly the ending - that meant it was virtually impossible to continue on with the series, without changing it quite significantly.
However, if it's looked at as a stand-alone movie, ignoring the book entirely - it's not too bad. It's got a couple of decent actors in there, some good moments occasionally, but it doesn't jump out at you.
In summation; if you've come from the book, it's going to be a big let-down. Movies-from-books usually are, but more so. If you haven't, it's alright, but nothing special. I'm hoping for a re-attempt at it in a few years time or something.