I have used a zune a few times but do not personally own one. From what I have seen I think that it is a good interface but poor at navigating through it with the clunky buttons. I am not sure how the battery life is or the software on the computer works well as the iTunes does with the iPod.it will take some time to mature.
Been a while now since the Zune was released, and I haven't really seen many people with it. I guess Microsoft failed to market it's product properly, or perhaps it just couldn't compete with the iPod. I think they came in too late with the Zune, since by the time it was released a good # of people already owned the iPod and it didn't make sense to them to buy the Zune as well. Perhaps if it had a lower price tag then people would of sold their iPods and got a Zune instead.