.since my .02 can be considered biased, perhaps some others will chime in here as well!
Well since you asked...
We used to race one at the LOORRS National level, my .02...next to Pro 4 and SuperLite
this was the best class out there but once they were moved to the Regional level we sold ours basically because we wanted to stay in the big show, if they were still at the Nationals we would still be racing one.
OK, that disclaimer said as long as you keep the engine and the oil at the correct operating temperature the SR1 is bullet proof, the Wellers did a great job designing the concept. They work great in places where you can the engine stretch its legs like short course, open desert/race, dunes however, if you want to race WORCS then it depends on the track. SpeedWorld-good, Utah-bad.
Like Corry said, AZ has a better car count than SoCal..for now but both series are continuing to grow plus there there is the SR1 Championship that pays ca$h.
Also, unlike most race vehicles of this speed and horsepower/weight ratio the SR1 an be used as a race car and play car and depending on how you lay out your interior it can still be a 2 seater which is nice.
I know Jim from Cognito was selling his SR1, heard Gary Thompson (motogary) may be interested in selling his, and there is one F/S in the Race Dez classifieds.
Last, if you're in San Diego go by Black Rhino and talk to Kenny Osborn, he has two of them in his shop you can check out and he supports the Regional series as well.
Hope that helps