I have now tried the stock seat with the show chrome (aka smart mount) backrest, the mustang seat and now the ultimate mid rider with the driver back rest. I also have the kuryakyn pull back risers and mini floor boards. After some modifications to the show chrome back rest that setup is the best but it still hurts the bottom of my legs after a couple hundred miles. The mustang seat is the worst because I'm bent over due to no back rest and it feels like I'm squishing my liver. The ultimate has me up so high and close that my windshield doesn't work (large clearview) and the drivers back rest is very uncomfortable pushing on my mid to upper back. In order of comfort for me (6' 1" and 32" inseam) is from best to worst:

Stock seat with show chrome back rest modified and risers
Ultimate mid rider with risers and no driver backrest
Mustang seat with risers
Stock seat with risers (no back rest)
Ultimate seat with back rest and risers

The good news is I have become very good and fast at changing seats. The bad news is I've spent a fortune and now I've screwed up the padding on my stock seat while trying to modify it for the bottom of my legs. I'm about ready to punt and sell the whole damn thing.