I have the Merker 39C, the one they call the Sledgehammer. I use it mainly when I've gone a few days without shaving. It really mows down the long stuff. Sometimes I'll use it for the first 2 passes and then do the last pass with my Weber and touch up with an older Schick injector. Great shave.
We'll I finally used my R41, I don't believe i will be trying anything more aggressive then this one anytime soon, but I did enjoy my shave with it, nice and slow no pressure, about half way through I stopped being afraid of it and had a good shave. One baby weeper, no irritation at all. 3 passes. Loaded it with Crystal Platnium Blade. Used The Art of Shaving unscented pre shave oil, Which I thought was a little thick but worked well, Truefitt&Hill 1805 sample I got from TSD, very nice, and finished off with CAPTAIN' CHOICE BAY RUM which I love. Was a good day. I'm glad I got this Razor.
Here is my review of the 2013 R41 version. http://theshaveden.com/forums/threads/the-2013-r41-rose-gold-razor.35058/