Only reason I still use 2 over 3 is that 2 gets the job done, is well supported and I don't see a big enough reason to move to 3. If 3 had a big performance increase, then maybe I would switch. Anyhow, I'll probably move to 3 at some point just because at some point more people use it (more code on the Internet in 3, more StackOverflow answers in 3 etc.)