I have a 1858 Remington Replica - what a blast to shoot!!
They really aren't THAT bad to clean - especially if you shoot Triple Seven powder. I was at the range last week with mine - fired off about 50 shots or so. When I got home, I took the grips off (1 whole screw), put the cylinders in a Simple Green/Water solution to soak, and put the frame in a pan of hot water. Then I scrubbed the frame with a toothbrush and ran a bore brush thru the barrel a couple times and the frame was clean - just a matter of drying it off and oiling it for storage. The cylinders take a little more work, since you really need to take the nipples off to make sure they are cleaned well. I got a little cheap Ultrasonic Cleaner from Harbor Freight ($30) and I use it to vibrate the cylinders clean while I work on the frame - not a bad little set up. So overall cleanup time was about an hour - and I usually work slow on my cleaning too.
As far as ballistics go, I'm getting close to 600fps using .454" round balls and 30gr of Pyro P or 28gr of 3fg Triple Seven. It is real accurate too - 6 shots will eliminate about a 2" circle of paper off of a target at 10 yds.
They will also hunt if you so choose, my son took a 140lb boar using 180gr conical bullets in it with 30gr of Goex Black.......... 1 shot cut all the way thru the chest cavity and then thru the opposite leg as well - took Porky right to the ground.