That is exactly the reasons why I'd want one. I have 35+ acres backing up to a hill with lots of rocks EVERYWHERE ... up the hill and down into the pasture. The don't call it The Rockies for nothing. One of these days, I'll be carving switch-backs up the hill, and a thumb would be ideal.
It looks like the L39 will be a good fit for me (could use a bit more hydraulics), but I do wish it came with a hydraulic-thumb mount (at a minimum) much like the B26 and M59. I had posted another thread on this a while back and under a different username, but the dealer I spoke with was talking about welding the mount onto the dipperstick and installing something like the U25 thumb on it. I can see how that could be possible, but still it seems like it could potentially lead to problems if it wasn't done exactly right ... alignment issues, popping-off the mount due to poor weld or too much hydraulic-power. Maybe you guys can share your thoughts here.
I'll look into the Addington. The 110 has a mount already on the dipper though, right? Despite the 110 being a preference, I haven't looked at it much because I've been under the assumption that it'll cost a lot more than the fully-loaded L39 that I want. I ran the "build your own" tool on the Deere website, but it was showing something that was way out of my range.