As far as memory protection, can you tell me honestly that it's turned on by DEFAULT? Probably not because it introduces incompatibilities with some software. While it's there and it's a feature, it's not like saying you have VIRTUAL memory. The classic Amiga didn't really have memory management and most programs were well written and didn't need it..
As far as MP goes, the more or less general consesus among us AROS developers is that it will take a completely new API to be taken advantage of for real. It just makes no sense for apps to be able to protect some memory areas, and then leave the backdoor open for other apps to come in and mess things up.
As for virtual memory, just a couple of days ago I've implemented the needed (small) changes to exec to allow for a custom memory subsystem to be implemented which provides virtual memory. This feature is currently exploited by the linux hosted flavour of AROS, which can now use the host's virtual memory mamagement to implement virtual memory for AROS.
As for no media player, don't you really have to go out an buy Frogger for OS4 to get a good full featured media player anyway.. Seems to me there are plenty of PD open source Amiga players that would be a simple port to AROS..
We don't have Mplayer (yet), but we have a commandline app, named "play", which uses the same codecs mplayer uses, which can therefore play back anything mplayer can.
Oh and no debugger? Do you as an end user of an operating system want to really see a debugger? Probably not, it sticks out like a sore thumb when it comes up saying "this is not professional"... So I really think that's a minimal thing..
AROS does have an integrated debugger, though. Or rather, it integrates perfectly well with gdb, when running hosted. The ability to run AROS hosted is something that we, as developers, could never ever get rid of. It's just too useful to be able to backtrace into the living or dead AROS, together with all apps loaded.