CS6 but I'm just learning how to use it. I've been playing with PS for about 15 years. I started with a 1998 version called 'Business Edition' and moved up from there. Amazing technology. If you can think it, you can do it with this program.
Have you ever looked at a website called Worth 1000? http://fxb.worth1000.com/
It's a contest site where people submit entries they did on PhotoShop.