There is now a fantastic high-definition "panorama" of the rock face at Craig Rhosyfelin, made by Adam Stanford and using Gigapan technology. Take a look at it here:
You can look at the whole face exposed during the 2012 dig, and you can also zoom in for high-definition images of the bedrock, the clutter of broken rock debris, and the "abandoned orthostat" which MPP thinks was intended for Stonehenge but which never quite made it.......
It all looks entirely natural to me, although of course the pit on the extreme left-hand edge of the photo is more convincing as a man-made feature.
If you sign up for a free account with Gigacam, you can take snapshots too. Unfortunately, they are not of very high definition, but you can also use your own "snapshot facility" on your own computer if you want images of better quality.
Above is a snapshot of the side of the "orthostat" -- where some of the marks are thought to have been man-made. The horizontal gouges and scratches appear entirely natural to me -- but it may be that the archaeologists are homing in on the two very faint vertical marks which are almost parallel. If you look very carefully -- and enlarge the photo by clicking on it -- you can see one mark in the centre of the photo and another to the left of it.
Not much to go on -- if I was wanting to argue that this is a quarry site, I would want rather better evidence than that.... so let's see what MPP and the boys and girls come up with.