Yes, DR was involved in the development of it, and did most of the work. GEM was also on the PC as well, but GEM on Atari was much better (And in my opinion, while not as flezible as Workbench 1.3, the interface was a lot cleaner).
I never noticed many problems with my STe in terms of running older software, but the advancements were definitely underutilized. I have to say, though, in recent years, the Atari ST scene is far more active than the OCS/ECS Amiga scene. (Well, okay, half of that is probably owed to BITS...which basically means nothing). As far as trackers go, in my experiences, Octalyser on the STe just blows away ProTracker, expecially if you like to play with the music in realtime. You can sort of DJ it, in a sense.
One thing's for sure, it's a hell of a lot easier to do a decent RAM upgrade on an ST/STe. Well, in my experience. And I don't mean a measly half meg. I've upped every ST I've owned to 4MB....but as for my A500...best I can do is 1.5 meg. Considering I want a running Amiga mostly for animations in DPaint III, 1.5 is not going to cut it. Having the entire OS in rom was also a nice tough as well, on the ST's part.
That Amiga in the trashcan is slowly being resurrected into a fully functional system. I just trashed the floppy in it and fitted a Chinon FZ-357 in place of it, and spent most of my time just making it still look like stock. The replacement keyboard is on it's way...now I just need as much internal fast RAM as possible, and a mouse.
That is definitely not Doomy's voice in that video. That voice is my own. I'm moving back to Washington state, so I might pay ol Doomy a visit, with a black sock and a roll of quarters. That guy got VERY....erm...impolite is an understatement. He got pretty insulting when I asked why he was trying to charge $200 for floppy drives. Despite what he claims wont ever work, my FZ-357 works pretty damn well in my Amiga...and it cost me one dollar.