@bloodline/all:
if you're happy with UAE by all means, use it and quit griping about MOS since you're not going to use/buy it anyway.
As far as what Amiga OS software runs on MOS, there isnt a definitive list. Do you think MOS Devel sat down and installed every single application to verify its compatibility? No, thats not their job. itix answered it well, "MOS can run system friendly (RTG/RTA) Amiga software starting from Kickstart 1.0".
The years long whine "I can get an (insert cpu) and run *UAE at (insert speed factor) times the speed of (insert system)". Well then go get it. I dont see you spending any money on any Amiga hardware. (Refer back to my first sentence up top). I bet you didnt even buy a AmigaOne when it came out. (refer back to my first sentence up top)
So it all boils down to...you wouldnt buy MOS even if it was for $125 because then you'd need an EFIKA, a case, a graphics card and a hard drive...and you'd whine about that too.
EDIT:
The EFIKA runs circles around the best, top of the line Amiga. You want a compact OS like AmigaOS, well its arrived.