If you're prepared to spend a little time customising a Linux environment, I believe you could get close enough to the appearance of a real Amiga.
My Amiga Forever 2005 arrived yesterday (thanks AmigaKit!) and I've not had any luck with the self-booting environment on my Athlon64-based machine... It hangs on detecting SCSI devices, and if I boot Knoppix with the "noscsi" option, the emulated Amiga environment loads, Workbench appears, then the entire machine appears to freeze - no keyboard or mouse movement...
I'll try it on my other PC later. Anyway, the self-boot option isn't 100% critical for me - I usually run WinUAE anyway.
- Ali