I'm still new around here but from what I've seen a lot of people seem to look down on MAME machines. I could be wrong, it just seems that way to me. If that's the case what's the big deal with them? I plan on building a clean MAME machine to add to my arcade, since I like so many games it would be impossible to have them all in my garage so this is the best alternative in my eyes.
I've got no problems with mame, multi, etc. - when like many others have said, it's done 'right' - and I'm sure opinions vary when it comes to that definition. Personally, I like the idea - it's given life to cabs that otherwise would be destroyed, it's brought people into the hobby who normally would not have gotten in, and it gives many people the chance to play obscure and rare titles that they may have never had the opportunity to try otherwise.
'Right' to me would be to multi cabs that are conducive to it - cabs that perhaps already have the correct controls or are a game that is included in the multi, or a cab that really doesn't have too many options - like too cost prohibitive to restore, etc. No one should take a nice working classic and rip it apart for this purpose, but everyone has reasons to do whatever stupid shit they feel they want to do to their possessions...
And to me, a correct mame build would be one that is set for a certain control layout done in either a generic cab or one that would have otherwise been destined for firewood\crusher. The biggest complaint I hear about mame is the obnoxious control panel - trying to squeeze in controls for *every* game imaginable in a space that is either too small, or building the cp into something that looks like a dining room table. Pick a set of games you want to play and build a mame pointed to that.
There is a lot of mame-hate here, but if you're really serrious about it there is always
http://forum.arcadecontrols.com/ - a community primarily for mame.