Only got Sam and 4.1 on Monday, so it's not fully configured to my liking, but I'm already very happy with it.
4.1 is an improvement on 4.0 which was an inprovement on 3.9 etc.
So what's not to like?
Put that on hardware significantly faster than my A1200 BPPC like Sam and life is rosy.
Admittedly Sam is pricey compared to other systems but is is cheap in comparison with other Amiga models of similar spec.
Compatibility with 4.0 wasn't an issue with 4 versus 3.9 for general use software in fact it became the other way round.
Some apps started to be developed for 4.0 only.
The obvious acception to this is WHD (A great proggy)
I used the dual boot option same as others mentioned.
I'm told there are ways to use WHD under emulation EUAE, I think.
I will test this to see if this is a feasible option for Sam.
If not, It's not a big issue as I will be keeping my classic system anyway.
