I can't justify moving to AOS4.x for 2 reasons. First, the PPC platform doesn't have much of a future. Even Apple dropped it. Second, hardware is, hard to get, and if you can get it, is quite expensive. The reason I got into the Amiga back in 1986 was because of its bang for the buck vs Macs and PC Clones.
What I like about AROS, is that it is more responsive on the same machine compared to Windows XP, Vista or 7. I have my AROS installed on a Dell GX280 3.2 GHz CPU, 2 GB RAM, 80 GB HD, AC97 Audio, NVidia GS8400 PCI-e Video, 3Com Ethernet card, which I picked up for nothing and it flies. It even does Screen scrolling like the old Amigas.
It's not complete yet. I'd still like better printing capability. But it is progressing very rapidly now. And there are two good distributions, Icaros Desktop and AROS Broadway. Also, it is being ported to 68K platforms, so not only will it work on upcoming NATAMI, Clone-A, etc..., but even on old classic hardware.