It's definitely one of the weakest of all Disney's animated films. I saw it in a theater opening night, and people were walking out halfway through. My friend and I stuck with it, hoping for the best, but at the end my friend summed it up well: A lot of good ideas that don't add up to anything.
Boring heroes. Boring villain. Boring magic. Generic everything. Zero world-building. An irritating attempt at "comic relief" that would only be dethroned by Jar Jar Binks.
A few good moments and some nice animation. I personally prefer it to Robin Hood, The Aristocats and Chicken Little, but it really is a weak film--an example of a good idea ruined by too many cooks. A potential gourmet meal turned to unflavored oatmeal.