I’ve been messing with Unity for about two weeks now. I’m using blender 2.56 for model creation. Seemed to work rather swimmingly. 
The first issue I really came up with was colliders not properly being generated. After messing with it for a while, I’ve come to the conclusion that this happens only when I’m importing an armature, as well.
Any ideas on how to get around this?
I know the armature’s interrupting whatever the “Generate Colliders” checkbox does when it’s checked, because I tried importing a version of the model with the armature deleted.
I also tried importing from a 2.49 .blend, it doesn’t work, either.
Not sure if this is the problem but i think “generate colliders” only takes your mesh and uses it as a mesh collider. This most likely will be a problem if your mesh is influenced by your armature/rig. If you need stuff like hitboxes or colliders for a ragdoll, you better set them manually with primitive colliders in unity and disable that “generate colliders” function.