Wonderboard behind acrylic surround?
I highly recommend not using drywall.
Here's my experience. almost 30 years ago I installed my 1st 3-piece tub surround in my bathroom and did it over regular drywall. I eventually had moisture problems (after a few years), and after patching things once or twice, I eventually redid it using water resistant drywall (something I didn't know existed the 1st time). I was very careful to "do it right" this time.
Well, I eventually had moisture problems again. It may have lasted longer then the regular drywall, but I was not impressed. It's not like this stuff failed immediately, but I think bathrooms should last more than 5 or 10 years.
About 8 years ago, I completely redid that bathroom again. This time I used cement backer board and put up another 3-piece kit (I prefer the surrounds over tile). I've learned my lesson, and will never put drywall in a shower again. The cement board is a little more work and a little more money, but well worth it.
Edit: I just wanted to add that my tub/shower was on 2 outside walls (an outside corner), so the drywall was sandwiched between a vapor barrier and the tub surround. Any moisture that got into the drywall was going to have a real hard time getting out. You may have better luck if your surround is on inside walls.
Last edited by wrongdave; 01-14-2013 at 03:53 PM.