I have a Zune HD, which (as I understand) is roughly equivalent to an IPod touch. There are pros and cons; the biggest two cons for the Zune are:
1) A tiny catalog of apps (compared to IPod), and
2) There are zillions of IPods out there, so everything is compatible with IPod.
For example, I got a new car stereo today. The first few I looked at were exclusively IPod-compatible, but I got one with a simple headphone jack input so I could use it with my Zune. When I picked up my car, the woman pulled out her IPod and showed me how it could be plugged in to the USB port . . .
Frankly, I don't feel a real need to control my Zune with my car stereo buttons, so this isn't an issue. And I'm pretty happy with the Zune HD. I'm told that the Zune interface feels awkward to someone who's already familiar with the IPod interface, but it seemed pretty natural to me. In fact, I still haven't gotten around to reading the manual about how the interface is supposed to work.
Now, this will seem weak- but beyond the two serious cons, I know there was a serious pro for the Zune, but offhand I don't remember what it was.