No regrets.
My 1,1 Mac Pro is still awesome. Just updated the processors to BESL mod 8-cores 2x1.86, jumping the speed a good 50% or more. Of all Apple computers I have owned across 30 years, this is by far the best purchase and the best value. It will be good for another 3 years I believe, at least, even if the OSs ditch it.
I got it with a couple Cinema Displays and have loaded with with better graphics card, loaded up drives and 16GB memory, and it's quite a beauty. The only problem I have and have had for a couple years that my main monitor is flakey after start-up or wake and it will black out, so needs unplugging and replugging to reset something there. Annoying, but 5 seconds of hassle every day.
It comes out after 7 years to about $1300/yr. for a computer. You could equate that to buying a new, lower-end iMac every year, but the power and convenience wouldn't be there, and I can probably keep this computer well beyond 7 years and use it for auxiliary needs.
No other "Pro" (I've had 7 top-end Macs across 20 years) has come close to being as great as these modern Intel Mac Towers. I'd regret buying a Mac Pro NOW, since the upgrade will almost surely appear within 6 months and the next Mac Pro will probably be quite incredible.