Well, if I felt like adding to the money I had already paid for Cinema, plus plug-ins, and the time I’ve spent learning the program, then $500 might be a good deal. I think this should appeal more to people who are just starting in 3d and haven’t dropped any dollars on their software yet or people who actually dislike Cinema and are looking for a reason to switch (traitors!).
The most tempting thing I can see there is an opportunity to learn the basics of a more-widely sought-after 3d program (is this true?), but then I’d rather go for Maya PLE, watermark or no, because I’m still going to do all my real work in the program I already bought, and Maya skills exceed XSI skills in terms of marketability (not that I’m anything more than a hobbyist).
That said, if I was looking at my first 3d software investment, this would be tempting…