One unified OS for the future?

[Fats]

If you ran a Workbench replacement like Dopus Magellan, chances are you'll prefer Ambient, if you used Workbench with some add-ons, you'll feel more at home on OS4.  Of course, you can run Dopus Magellan on either system as well.

Just down to taste really.

Exactly, I was always a workbench + VincED + Dirwork user and I prefer OS4 Workbench over MOS Ambient. That's also why I think an unbiased comparison is impossible.
From the other side I do think MOS has some better technical lower level implementations compared to OS4 so as the latters use of .so objects.

[Fats]

The only .so files you find is the onces ported from Linux. And having .so file support most defiantly helps poring over software like QT, hey if you don't like software that is ported from Linux your free to stick to only MUI and Reaction software, but chances are that even they contain linux libs ".a" files that have been linked into it.

I don't have problem with porting Linux software. I have a problem with run-time linking which makes program startup non-instant which in my eyes is not Amiga-like.
When I start a browser on my A1SE it takes a few seconds to start up.
You should also find more info on this site and on the AROS dev archives on why I think that everything where they use .so now for - including plugins - can be done using amiga style shared libraries using compile time linking.

Simply put "shard object" support is a compromise.

In my eyes a bad compromise: it trades off user experience for developer comfort.
Of course all in my idealized definition of what an Amiga OS should be.

[Fats]

The "Look and Feel" justification is one of the easiest differences to point to though, so it is often mentioned.  I just hope it is not really true that users are making their choice on the "Look & Feel" factor, when it can be adjusted so easily on either OS to "Look and Feel" any way they like, even almost exactly like the other OS they are turning away from by making that decision.

It's very difficult to really put the finger on it and it's likely more than just look & feel but the whole behavior of the system. And yes I did try to change the look (it was already a year or so ago so not the recent MOS version). If it really can be done it is not as easy as you seem to try to point out.
One example of look I can't get used to is the button style interface to switch between multitabbed shells; I did not find a setting to transform that in tabs as GUI element.
All said I do enjoy using MOS less than using OS4, although I hardly use any of the two lately. You may find it irrational and I have to admin it is subjective. I am also one of the guys who thinks DirectoryOpus went the total wrong way with version 5.
If you want to call me ignorant because of this I think we have to disagree.

Edit: This is in no way an attack on people who do enjoy using MOS over OS4. I can fully understand that and please do enjoy it; just realise other people may think differently and you will never understand them

[Fats]

I must admit, I'll be highly impressed with Hyperion if they can successfully implement smp and memory protection while remaining compatible to current apps.

There are those who claim it's impossible, and famously even Apple tried and failed with Copland.

One of the main things that is a problem is that Forbid() is not SMP friendly. When a task calls Forbid() it expects no other process will run at the same time also not on another CPU. Currently this function is used a lot both in the OS libraries as well as in programs themselves.
So one of the things being done is to replace Forbid() locking in the OS functions with other means of locking. Likely this will break compatibility with some programs that expect the exact Forbid() behavior. This in turn will be enough for some forum whiners to claim the result is a not 100% compatible system but for more pragmatic persons it may be good enough as most of the programs will still run without problems and also giving you the advantage of SMP.

This still leaves the programs that themselves are heavy Forbid() users. This can likely be solved by penalizing the performance of these programs by rate limiting Forbid() calls so non-heavy Forbid() users are not much impacted and run (almost) at full speed. Probably enough material again for some people to complain loudly.

[Fats]

You mean users are stupid trolls, right?

No, the people who are not user but use the fact that one or two programs don't run or have to be run in UAE to put rants on forums are the trolls. The users should use the OS they enjoy the most; hobbyist devs should work on the features they enjoy the most.

[Fats]

AmigaOS uses cooperative multitasking with a preemptive scheduler. Where it falls short of the definition of preemptive multitasking is memory protection and task protection.

What a very strange definition of preemptive multitasking...