Since quite a few people have mentioned liking Ron Paul I thought this part might be of particular interest.
The only dissenting vote in the short House debate on the bill was voiced by GOP presidential aspirant Ron Paul (news, bio, voting record) of Texas. He described the bill as "a flagrantly unconstitutional expansion of restriction on the exercise of the right to bear arms protected under the 2nd Amendment.
I haven't had a chance to read the bill myself yet, however taking into consideration that the NRA is supportive of it, it's likely to be pretty decent. I think the reason for such massive support is due to the need to restrict access to fire arms to individuals who are mentally unstable, the arguments aren't really if we should do it but how, and that seems to have been hammered out for the most part.
My understanding thus far however is that it would allow without any legal process doctors to place someone on a ban list... which effectively means the persons right to own a firearm would be denied without due process, which is why Ron Paul was in opposition to it, and I can't say that isn't a legitimate argument.