It shouldn't matter if all the machines are running the same OS... The commonality here is the Ethernet...
I ran a mixed system with it years ago... But that was before running everything 64bit...
What posts I have found claim that it works fine in 64 bit OS...
Remember that regardless of how much memory you have in each machine, the 32 bit stuff is still more limited to what memory it can use, so memory beyond the 4G limit to 32 bit OS will be the limit of what it can do... The good part is that you can add lots of machines and distribute your plugin's around them all as necessary...
As subtle hearts mentions, I too have so much memory and processor power these days that I no longer need to do this, but it's handy to have around "just in case"... ;-)
Keni