It's possible to delete the game data to undo the patch but there were some problems with the unpatched version, obviously, since the patch was necessary in the first place. I think the game was patched more than once and it's not possible to choose a previous patch, as far as I know. It's the latest version or nothing.
I can't remember how it all went down but I think there really weren't any noticeable problems with the first patch, unless you count the multiplayer stats problems and such but I think they were fixed without a patch on the user's side.
It's all pretty confusing and frustrating.
- The Artist Currently Known As Jeo.