My thoughts on this topic are quite mixed.

Bugzilla is no place for casual enhancement requests. It looks too complicated to non-technical users and it would really need some tweaking to be userfriendly. And then I don't think bugzilla isn't the right place for non specific requests.

I really like the simplicity of brainstorm. It seems to have a low barrier for non-technical users. But this is also it's main problem. The sheer amount of duplicate and thus useless requests will be overwhelming pretty soon. There would need to be a lot of triaging.

With my webmaster hat on:
The nightmare of yet another system with it's own accounts is something I will loose sleep over