Badly. Guys like Bendis wouldn't know how to handle a guy like Superman, and I honestly feel like Marvel doesn't have the right attitude or writers to use him properly in the way DC does, which really is the best way imo.
With Superman being SUPERMAN.............I find it hard to helieve that Marvel would be THAT disrespectful of the worlds most well known superhero and their fans.
I can see some writers using him well. It's editorial you'd have to worry about, imo.
Considering the buzz such an acquisition would cause, I'd doubt Marvel would job him out or bury his character out of pettiness instead of trying to market the hell out of the guy and rake in money.
It depends entirely upon how one views Superman. Is Clark the mask or is Superman the mask? Personally, I don't think Superman fits in with the concept of the Marvel universe well.
Also, creators and editors work have worked for both companies so they know who characters are regardless of the logo on the cover. Just depends on how heavy handed the orders from the top are and whether they lower his standing in relation to other well-known Marvel heroes.
If the TC is looking for battle board stuff then its basically, Superman is Superman and everybody knows this. He'd still be a top tier ass beater.
I really don't think so. Maybe someone like Bendis would because he's an ass, but you have several people who have worked for DC prior to joining Marvel in addition to plenty of writers actually liking Superman, too.
I can see them making Superman stalemate or have inconclusive battles with the likes of Hulk, Thor, or Surfer, but I don't see them trashing the character just for battle board purposes. He'd instantly become a top draw and shitting on him wouldn't help them financially. Sure, jobbing would inevitably occur (as it does for every character), but the reality is likely that Marvel would instantly begin to make their universe be molded around him.