Since I've used the Carbon for 3 days, I'll contribute some throughts of my own too.
I love my Jukebox 3, but after using it for 1 year & half, I really wanted something small that I can carry around with in my pocket without feeling too much the power of the gravity.
I bought Carbon at Bestbuy few days and I was very impressed with the look, feel(small yet solid), and the capacity of player. However, I have to say I wasn't happy at all with the sound quality(I use ety er-4s), the custom equalizer built-in is very nice, but no matter how I played around with it, it just sounded very "screechy". I don't know how powerful the built-in amp is but it really sounded like it was having a very hard time driving my headphones...
Also another missing feature turned me down is that it does not support Chinese display(only French, English & Japanese i think...), so if you're a Chinese and has many Chinese songs, I wouldn't recommend it.
The OS in the player is also buggy, I put 30 songs in my "favorite" playlist, the player just put the songs I chose on the top of the playlist and the rest of the songs on the players beneath them(but still in the "favorite" playlist!)
So I just went out yesterday & bought a 20GB 4G ipod and I'm sooooo much happier now. For $50 bucks more, I get amazing interface, many many foreign language support, great sound(just a tad bit worse than the Creative Jukebox 3), great look, soso battery(Carbon lasts longer), and much bigger capacity and still small enough to fit into almost any pocket.
