I guess we have a variety of opinions here, don't we? Here's why we use Castrol... Its a unique formula that is less hygroscopic than any other fluid - it absorbs less water. Therefore, even when it has absorbed water its boiling point is still SIGNIFICANTLY higher than any other fluids wet BP. We don't like to work on our cars at the track. We don't have a mechanic that accompanies us. Any work we do - we do ourselves - its expensive for us to run 2 cars, so in order to keep costs down, we do our own work. We believe track time is for driving and prep and maintenance are done at home. So, jacking up the car, pulling all four wheels and bleeding the brakes at the track is not my idea of a good time - especially when either Henry and I are usually on the track every other session. While we may end up changing front brake pads, its just one less thing we have to do.
We ran three full days at VIR this year with no fade whatsoever. We did not bleed brakes during the event. So yes, the Castrol is about 3 - 4 times more expensive, but we did not bleed for three days. To us, that is not a waste. I will also say that running the Viper with the stock brake system, no true cooling ducts and track pads generate a TON of heat - so this may be the most severe test of brake fluids.
So, its up to you - I think using the SRF buys you something. If you want to bleed every day or (yikes) after every run, then don't bother with the SRF...