I could give you several very biased reasons why you should avoid the Zune, but the most objective one I can offer is they haven’t hit the streets yet and haven’t been field-tested by the masses. It could be the iPod killer, or it could totally suck. But it will be months before that’s decided.
Of course, the only person it really matters to is your stepmother. Since she’s non-technically inclined, the tech details will matter: how to upload/delete songs from the music player, what restrictions there are to each player, how to use the software each player is compatible with, what music service options are available to her.
I have a 10GB iPod and use iTues and find the whole thing easy. To upload songs, I can drag and drop mp3 or m4p files from my music library to my iPod. To delete them, I highlight the song in the list and hit Delete. There are basically only two restrictions to your song files: one, m4ps can only be shared among five computers, and two, you cannot (legally) copy music files from an iPod to a computer.
iTunes works perfectly for me, although I notice Windows users seem to have issues with it. I own both a PC and a Mac, but only listen to music on my Mac, so I can’t comment on whether the Windows version does in fact have problems. I do, however, know there are alternative software programs to iTunes, so it’s not like you have no choice but to use iTunes with your iPod. I assume your dad’s PC currently has song files-- maybe you could download iTunes and play with it for a little while and see if your stepmother can use it/likes it.
From what I understand, the Zune’s restrictions are a little more complicated. Users will be able to transmit music (no idea if formats other than mp3 will be supported) and photos wirelessly between Zunes, but supposedly there will be a 3-play or 3-day limit on the playback of these shared songs. Once the 3 plays or days have gone, the files will remain on the Zune but be unplayable. (As far as I can tell, it’s unclear if the files will ever be playable again, even if you’re able to download them to a PC.) Not a big issue for those who won’t be sharing music wirelessly, but it is a drawback unique to the Zune.
I would also consider the iTunes Music Store into the equation. Microsoft is supposedly planning an equivalent to the iTMS, but it’s going to be a long time, if ever, before its library of music and video approaches that of the iTMS. I know you’re not considering an iPod capable of video playback, but there may be music your stepmother wants she might not be able to get as easily as she could from the iTMS. And since iTMS files are in the m4p format, which only iPods/iTunes can play, if she gets a Zune, she won’t be able to listen to them unless she converts them to mp3 first… something I don’t think someone not technically inclined will want to do. Hell, I am technically inclined and I don’t want to do that.
Assuming the mp3 player isn’t a surprise, if you’re able to, you should take your stepmother to the nearest Apple store and go play with the iPod models on display. (If you didn’t want to install iTunes on your dad’s PC, all the Macs at the store should have iTunes installed.) After playing with them, she might decide she loves them (or hates them) and make the whole debate a moot point.