I use a program called XaraX (
http://www.xara.com/) for doing my buttons at home ... allows you to export graphics as 24 bit PNG's with 8 bit alpha so you can basically do what the hell you like with transparency or opacity etc.
I find it pretty easy to use but maybe if you're into PhotoShop then it might be unintuitive (personally I can't find my way around PhotoShop) and take a while to get into but the best thing is that as a vector graphics program you can resize and rejig as much as you like and your exported graphic will always be as crisp as possible.
Phil