I used Amsoil Racing 20W-50 last year and had an extremely good UOA (Cu was slightly high but due to break-in of engine). Was impressed except a little noisy. I used Amsoil M/C oil before the new blend came out and that was good and less noisy than the racing oil. I'm using Redline now and even less noise and my idle speed actually went up slightly (vs. the Amsoil TRO). I used the Harley stuff (several times) in my Sporty in the past and the engine did not blow up, but, for the price and the frequency that I change oil (once per year) I just can't see spending $4 for a product when I can get something that is so far advanced for $3 more. The difference per OCI is about $10. I noticed smoother running and cooler engine oil temps with the synthetics. That, to me, alone is worth $10 per year. When I am stuck in traffic for several minutes in the summer, I am glad I have a little extra protection because I know those cylinder heads are HOT.
I guess I am lucky because there is an Amsoil warehouse 5 minutes from my work and there is a Redline dealer 10 minutes away that sells Redline for very good prices. I do have an Amsoil "dealership" but I rarely sell to anyone, I just use it to buy oil for a discount. As you can see though, I think Redline is definitely a good oil and I just want the best for my vehicles, not to sell oil. I use Redline MTL in my primary and I'm using Amsoil in the gear box currently but will be switching to Redline Heavy Shockproof this fall. Mobil products are also good and I've used their MC oil and gear lubes. I've used Royal Purple and was not impressed and I haven't used SYN3 because I just don't think its worth the price.