Let's put this into perspective. Here is the spec for a current Mac Pro I'm considering.
2 x 3.0 GHz QuadXeon
8 GB RAM
NVIDIA Quadro FX 4500 512MB
2x750 GB 7200 rpm Hard Drives
Bluetooth + Airport Extreme
Mac Pro RAID card
This comes at the bargain basement price of just £6014.99
Now come 2011, I should, as far as I'm concerned, be able to upgrade my damn OS. And if anyone suggests that in four years time the spec on this machine wouldn't be capable of handling a 'modern' OS is talking out of their a***.
Now let's go back to 2005 and price up a G5 for a similar amount of money. Yes, it would be more than capable of running a 2009 OS. And Apple, having taken that cash, should provide one.
We all have to live with the fact that technology dates faster than we'd like. Let's not rush the aging process any faster than needs be, eh.