I've had one for two weeks, and I think it's great. I have a black one, and the case is very durable--much less scratchable than the 30GB iPod or the Creative Zen Vision:M. I wasn't interested in the iPod because I wanted an FM tuner without having to pay an extra $50 to actually use it. So I was choosing between the Creative and the Zune. The Zune won because of its durability and the interface. Also the screen is larger and the text is easy to read. I have 9.7GB free on the Zune and it holds all of my CDs and some of my DH's (he can't find some of his).
I did have to exchange my Zune yesterday for a new one. It seemed to be defective--it would randomly shut itself off. But it's not a widespread problem, so I should be fine now. I haven't had any other issues.