Personally speaking, I'm an iPod user (old-school 6 GB Mini), and overall I'm happy with my purchase that I made over two years ago. But that being said, I don't think the iPod is the be-all, end-all MP3 player. Granted, you are probably going to find the most 'acceptance' with the player, with plenty of 1st party and 3rd party support for the player. But there are more than the fair share of hiccups and other issues with iTunes and the iPod itself, but it isn't so outrageously bad that I would advise anyone to go without it.
The Zune has been hit and miss, and I can't say anything specific about it since I have yet to use one. I only know a few people who have bought one (personally), and what I have seen of it, it seems like a decent buy. Would I buy one? Probably not. I hate DRM, and the iPod and Zune have those issues in spades. But most players do these days, and it really does suck. I wouldn't completely rule the Zune out, but if you're that much against it, by all means do so.
On the flip side, the Creative seems like a fairly good player that is wacky enough not to seem too 'trendy,' and seems to be well-accepted by the tech-savy public. I've only used one once, and I didn't find it too hard to use, although I didn't operate the computer software with all the music stuff in it. So I guess I really can't talk too much about it other than saying it lacks the 'locks' of the iPod and Zune, and will allow you to use a wider variety of music services if you choose.
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If I may ask, why do you need 30 GB? It literally took me two years to fill-up the 6 GB on my iPod, and even then, I'm about ready to go through it and delete a lot of the music on it, as I just don't listen to it.
iRiver has always been a favorite of mine, and I'd give them a thumbs up with most of their models. If you're willing to save some money and take a hit when it comes to overall capacity, the Clix is great.
But, shes only good for 2 GB, only shows video at 15 fps, and unfortunately is preparing to align themselves with Microsoft/Urge/MTV when it comes to music. Crap.
...Oh well. I guess you can't go wrong with an iPod then...