I love my thumbhole stocks! I shoot prone kneeling and off hand a lot. I prefer the feel of the HS Precision PSS120 and PSS046. The hole is smaller on the HS, but I just love the way it feels. I am short with T-Rex arms so I have it cut to a 12.5 LOP and add a 1/4 inch spacer on one for summer shooting in prone.
I also have a Manners GAT that I am not fond of the feel but it is for a WINCHESTER action and HS only makes thumbholes for Remington actions. I also have an Bell & Carlson thumbhole for a Win action, that I bought in a pinch when the Manners did not show up. It is nice feeling and to me feels a touch better then the manners, that is all I will say about it.
I live in Big time Grizzly country and feel that in no way does a thumbhole stock hinder anything other then when I have to off hand a grizzly I will shoot better! I shoot it pretty fast as well when needed, some wolves, numerous elk, a boat load of coyotes and a couple of bears do not like the feel of my thumbhole stocks though.