Yes, to me it is sometimes night and day between the back and the front, the front being always smoother. Before, I used to always go on the back for the airtime on a gravity group but not anymore. But hence why I did Mine Blower only one time and on the back row (should have done the front).Interesting list! Also, I find it interesting that you pick up on Gravity Group coasters rattling; the only one I've ridden is Mine Blower, and while it certainly wasn't the smoothest of coasters in the front row, I wouldn't have said the rattling majorly affected the experience for me, and I certainly don't have the highest of roughness tolerances by any means! However, it is probably worth noting that I only rode it in the front; is it really that much worse in the back?
At some point I thought I was just being picky after hearing everyone praising Gravity Group and me not liking them that much and even having headaches. I didn't have any problems with the GCI but I always got assigned to the 1st row for almost all of them. And then I did T-Express and understood what was a genuine smooth and exceptionnal wooden (front or back are both as smooth as a good steel coaster). So nope, I don't agree, Gravity Group is not that good and I don't know why everyone is so forgetful of their roughness. Either this or they are very moody coasters. Which wouldn't surprise me as woodens are always very moody, specially the badly maintained ones in China.