I have done 25 hours of test flying on a brand new RV10 with a thunderbolt and 3 blade carbon fibre Hartzell.
I normally fly behind a stock IO540 and two blade.
My observations;
Don't get it painted black!
No appreciable HP difference although there may be one or two.
Was very smooth and it may be partly the prop, but it was smoother than our engine by a small amount. And we dynamically balance ours, the test aircraft has not seen a balance yet so the engine and prop must have been good out of the box.
Lots more $$$, and even more so with the prop.
Would I do it, no not likely but each to their own.
YMMV