I had fun with ZBrush a couple of times when I bought it, despite the obscure interface and nonexistent documentation. Gave up on it after their horrible copy-protection system turned the program off for the 4th time in 2 years. Despite repeated promises to "fix" this, the company seems to enjoy playing "the good guys", sending out repeated fixes that never last more than 6 months. I find most mandatory registration programs to be totally obnoxious. Having to do so repeatedly is absolutely insufferable.