I would like to point out that with AmigaOS4 running on classic Amigas you can still use software dependent on the AGA chipset. However with regard to the AmigaOne hardware this is only the case by using the emulator E-UAE:
A Screenshot of E-UAE (based on WinUAE core) on AmigaOS4:
Demonstration video of earlier version of AmigaOS4 demonstrated by Ryu on his A1200 (28th December 2004):
Hardware specs: Amiga 1200 with Blizzard PPC accelerator card with the CPU clocked at 166 Mhz, 128 MB RAM and BlizzardVision (Permedia 2) graphics card.
AmigaOS4 on A1 hardware:
Older demo video from July 2004 (movie players):
68k/WarpOS emulation, etc, demonstrated from March 2005: