I'm not going to search which page it was on, but wasn't the concept that floated around was that of Norman being lost in New York? It seems to me like they could tell a new story while retaining the locations in the movie (apartments, sewers, sausage factory).
And I too liked the movie. No, it was no masterpiece (the sausage scene was a little cringe-worthy), but it was still pretty good. The only problem with it was that it didn't seem to have the emotional push you'd expect from a pets movie. However, anyone who ever loved an animal will probably find themselves shedding a couple tears during the last few minutes.