Hi, Frank - nice to see you back in the neighborhood.
The iPod's ubiquity, broad accessorizability, and "no-brainer" protocol make it emminently suitable for folks who don't care to get into the nuts-and-bolts approach to portable A/V entertainment. If one has a computer which supports USB and if one's musical taste does not stray far from mass-market, or at the least if one possesses or has access to music to one's taste which can be loaded to a 'puter, what comes in the iPod's box is all one needs. An iPod will play most formats, but only (theoretically, anyhow
) iPods will accommodate media downloads from Apple's
iTunes Store. Other portable media devices all have their own plusses and minusses, too.
What it comes down to is personal preference - read reviews, talk to users, go to stores and do some hands-on evaluation of the options.
Media apps such as Windows Mediaplayer, RealPlayer, WinAmp, and the like do not natively play well with the iPod's Apple-proprietary format, but work-around 3rd-party plugins of assorted utility/success abound.
All that said, personally, I don't have much use for any of those sort of portable devices; at best, their output comes close to resembling music. By and large, they're tolerable listened to via unimpressive headphones, but sterner playback hardware quickly and unforgivingly reveals their inherent shortcomings.
Sidebar: All else being equal, and X-Box notably aside, given Micro$oft's history of abandoning hardware, I put the Zune in the "Wait and see" category.