I have not played the rules yet, but have a few games of The Men Who Would be Kings under my belt. The rules are fast and fun. R&P looks to be a streamlined version of The Men (etc.). Only one officer per side instead of one per unit, less to keep track of. It looks like the body count will be lighter, it taking two hits at close range to knock out a figure, three at long range. All told it looks good.
My minor beef: some of the unit descriptions. But those are suggestions rather than hard and fast rules. I don't think all Confederates were armed with smooth-bore muskets while all Union troops had rifle muskets. I don't see woodland Indians as operating in big bands storming places with tomahawks. But then the rules let me create the various units as I see fit. The cinematic style of the rules do not require that orders of battle be taken from the movies.