Been looking at the MM's on EBay myself... But what exactly is MorphOS? I've read the website and I can't tell for sure. Is it a variant of the Amiga OS in some way?
MorphOS is an OS for PPC that is compatible to AmogaOS 68k, PowerUp and WarpUP applications. Several OS4 apps can be run by a wrapper (OS4Emu), which is kind of comparable to WINE.
Furthermore MorphOS can run MorphOS binaries of course.
The structure and layout of MorphOS is like you know it from Amiga OS 3.x. There is C: libs: s: devs: and so on. The foundation of the OS is exec and intuition and all the other libs and files known from Amiga OS 3.x.
MUI is prettywell integrated (and enhanced) into the system. Workbench has been replaced by a much more modern and MUI based successor that is open source: Ambient.
Many things have been modernized and optimizes, some things have changed. E.g. The prefs are now accessible by one app (still it is possible to access the seperately), or the system files are seperated in a better-don't-touch drawer called sys:morphos/ (inside that drawer there is c/ s/ devs/ and the whole shebang that is also available outside the sys:morphos/ drawer. You may mess with everything outside morphos/, but dont't touch sys:morphos.
And the best news: It is unbelieveable fast and you can try it for free!