You can get an oil analysis for about $25, it's worth the money if you really want to know the truth about synthetic oil.
I use Black Stone labs for my oil analysis. When I had the Triglide I would run the oil 5,000 miles like I've done with all my Twin Cam equipped Harley's. My oil analysis while using Syn3 have always come out great. I have since switched to Amsoil but haven't gotten any oil analyzed with it yet. I think next year I'll pull on on both bikes and see how they are doing.