Sam460EX is a way to give new HW (instead of clunky old one) to the AmigaOS, Altivec isn't used in Amiga software at the moment (with the sole exeption of mplayer) so it's basically irrelevant.
What's more to like is the faster memory interface, and the chance of going beyond PCI or AGP old-coot GFX cards (and yes new 3D subsystem and drivers to support all this are coming).
The whole project is very cool for AmigaOS aficionados, if you prefer something else go buy it, nobody will stop you ;-)
Ah! And to those who believe they have a better idea, go do it, you will learn the difference between talking in forums and actually bringing a real product to market.
Then if it's truly better people will buy it, so more power to you ;-)