Operation of Zen is the iPod Classic quite similar, only that here is navigated with buttons and not with the "jog dial" button of the iPod. Overall, the operation is the startup and shutdown might go a little faster at the Creative Zen, but is not really a downside.
The great advantage of the Zen is that you can manage it on several PCs. While an iPod is exclusively connected to a PC (if you try to connect the iPod to a second computer, it will attempt to delete the files in the iPod), the Zen can be easily synchronized with multiple PCs. Since I have my music files are for example. On my personal laptop as well as my work PC, I can play on Zen on each unit with new music. Also I can play MP3s from my friends without any problems on my player.
The included software is quite cumbersome. It is advisable, however, to use open source media player like MediaMonkey, which automatically detect the Zen.
All in all, the Creative Zen excellent and above all more economical alternative to the iPod.