I have a Rev A dual-2.0 G5 that I got in September of last year. Meaning it's pretty much got the 1st rev of everything in it.
I've had it freeze maybe 3-4 times, and I use it constantly. At least an hour or two a day, every day, and often 10 or more hours.
So, while I agree than many G5s - or many of any model - suck, it clearly isn't true that they all do, nor is it true that Rev A's always are bad. I've had no audio problems, no buzzing power supply, etc.
The only problem I've had with it turned out to be due to a fault in my 20" ACD.
I would continue to stick it out with Apple support. Bitch long enough and loud enough, and they will eventually make things right. In my experience (not with the G5 but with other Macs), they're at least as good as any other computer customer support group.