The above reviews are true but recently the southern half of the road has been resurfaced (mostly) and this has improved the road and experience.
carelesschuccai done this road from muirkirk to strathaven, it was a good ride when i had my mrs on the back as i took it easy, when i went myself i went a bit harder and the road is very bumpy, i almost ended up in a field a few times after leaning the bike into the corners only to hit a bump and run wide. overall a nice run but watch out for the bumps
"The Muirkirk Road" Starts off at the staggered junction in Strathaven onto very fast straight then a slowish left over a raised bridge.... and from there the fun doesn't stop. Fairly decent surface and open enough for cracking on.....until you pass Dungavel HMP(toot-toot) then it is'nt. From here to Muirkirk fitting a steering damper will not be far from your mind, whatever you ride .Never the less it is very entertaining.