Our house has an IPOD and a Zune. IPOD gets rave reviews, but the Zune not so much. It is EXTREMELY temperamental, the software only works went it decides it wants to and the car adapter is pretty much useless (and MS does not seem to be coming out with an alternative anytime soon). Of course, the bigger screen is a cool feature, but honestly, our opinion is that the Zune has a lot of growing to do to compete with the IPOD.
So, our house will probably be getting a second IPOD on the next gift-giving occasion. Save yourself some frustration - say no to Zune.