Having just watched Stuart Little 2, I was curious enough to watch Stuart Little 3. Just so we are clear: this is a direct to video movie, minus the live action. It is mostly 3D computer animated, although the characters look like they are animated in 2D, which seemed kind of weird to me at first. This is NOT a top quality animated film, but there are a few parts where the animation does look interesting. I see on Netflix that some people reject the movie because of the animation.
I am not so much worried about whether this is live action or all animated, and I am not too concerned about the cheapness of the animation. I am mostly interested in the quality of the story. The first half seems so full of promise. There is a lot of humor here and a few very cool moments. I think that the first half might be worth checking out. You can see all the best parts here.
The second half is a little dull. It seems like they ran out of cool ideas and therefor the movie mostly degrades into a kiddie story. That might be O.K., but I think that even little kids know the difference between good stories and dull ones. It is not terrible, but it is not that great either.