Best MP3 for Mac/Win/Ubuntu & work?

I’m sick of MP3 players not carrying over from one OS to another, or (like Apple), not transferring all the songs on my player to my work computer. So what i want is an MP3 that can work with four OS (XP, Vista, Leopard 10.5, Ubuntu 8.04/8.10) and will transfer songs from the MP3 player to the OS or vice versa.

Video playback is irrelevant; durability (workout use) would be a plus.

The Cowons should be fine.

My son has a Sansa Fuze and it works fine with Ubuntu and Windows XP and Vista.

Basically you want an mp3 player that can do mass-storage (or MSC) mode. With that, it acts like a hard drive and you can drag-n-drop.

I have a sandisk Sansa that will work with any OS that supports USB mass Storage Devices. Also, there are programs that will load songs on an iPod from Linux, may want to seach sourceforge on that one.