Another benefit of the iPod over the Zen is that it was discovered that the iPod battery can be replaced by yourself (by buying the battery for ~$30 and installing it yourself through instructions), but I have not seen any methods in replacing the built-in battery in the Zen. These units will last for about 2 years, so once the battery starts to flaw, you'll have to get Creative to replace it for you (which'll cost money, not sure how much though).
Then again, there's still a lot of future players, and eventually maybe a company will release one where the battery is easily replaced, is compact, has great sound quality, is easy to navigate, and is not too expensive. There's even video players coming out. Music players ought to become very advanced soon. Someday the ideal MP3 player will come, so I'll have some patience for now..