I'll get a Zune when Microsoft admits that the Zune was the backup plan for replacing Windows Mobile, and that they've been taking their time because they wanted to make the transition worthwhile and do app accessibility and multithreading right.
If that's not ever going to happen, I won't ever get a Zune. But who knows what Microsoft will pack into future versions of Zune... I might reconsider.
What I want, as a developer (albeit, a tinkerer, but point being not an end-user), is productivity application support, not just games development support. I'm very happy that XNA now supports Zune, but frankly I don't know who's interested in that except for Microsoft. Now if Microsoft can expand on this API set and make XNA for Zune support productivity applications development as a whiz-bang PDA platform, I'd go super-nuts with it.
More specifically, I guess what I'm looking for is a set of practical, nice-looking, and responsive UI controls, a rich networking stack, an integrated browser API (a la webkit but I guess using IE Mobile), appropriately categorized app accessibility, and the packaging and branding of a small, lightweight device, not a heavyweight song-playing brick. Also need multitouch if XNA 3 doesn't already have it, I haven't checked.
I want these things because I'm still in love with my yester-year's news iPhone, and XNA development just does not compare with iPhone development. iPhone isn't about games, it has never been about games, even though iPhone has an awful lot of games running on it.
And of course I'd be absolutely happy if it went the other way around, if everything on the Zune ended up on Windows Mobile as far as the developer is concerned (i.e. full support for XNA 3), as long as the Windows Mobile UX is still overhauled. I just always hated the Start menu on Windows Mobile, and I LOOOOVE Zune's UX although it's suited specifically for entertainment and not productivity.