* What is the level of Amiga OS3.1 support?
It is OS3.1 API compatible
* Can it run WHDLoad style games? (be gentle with me here!)
No, that would require UAE because EFIKA, Pegasos or Mac Mini has no Amiga Custom chips for old games if they don't run on graphic card.
* What is the Native application support like? (Office type, Web browser etc...)
There is Papyrus, Sputnik and some other stuff like MUI4, CyberGraphX 5, Poseidon 4,...
* Is it quicker than say 3.1 on an unaccelerated A1200?
Compared to what hardware? EFIKA, Pegasos, Mac Mini?
