I had a iPod nano for about a year, before the screen worked. I had hacked that thing to hell, too. I had ipod linux on it, had doom installed, and video working just fine, before there was a ipod nano with video. It was pretty nice.
After it broke, I was without an mp3 player of some time, and saw the zune on sale for 90 or so bucks at radioshack on black friday. So I picked it up and have been enjoying it for almost a year now. Microsoft keeps updating even the older ones like mine with the new firmware so all the zunes get updates and features regaurdless. I just bought a zunepass and have been downloading entire albums like crazy. It's fantastic. Can't wait to see what else is coming.
I like them both equally, I guess. It's hard to say.