It runs 68k applications under emulation (2 or 3 times of a real speed of a 68060 on a ppc 604/200). It is a serious project as it follows AmigaOS use and ports unix apps. It is like AmigaOS4 but it is here (not at beta versions). You can download it for free. It plays mp3s, it has nice internet browsing support, it also has advanced networking options, finally it is an excellent choice for PPC equipped Amigas due to it's native PPC code.
P.S. you can find recent libraries,freeware,shareware and long awaited ports in Aminet.
This is the only recent OS we have on Amiga side and follows the steps of MacOS-X (PPC side) as WindowsXP are out of the OS competition (2 years now).