@Red Beard - The point was already made by
@goody94 ... the first hurdle is obtaining a good leg loop for your thigh. Without it, the ascent is quite a bit more difficult, as noted in previous posts. I think that stops a lot of guys right there, because thigh loops aren't commercially available. I improvised one. I had an old rock climbing harness that wasn't getting any use, so I sacrificed it and cut off the excellent padded leg loops from the waist band/belt, and presto! ... instant padded thigh loop with carabiner clip-in point attached. The next hurdle for me is time to practice - I haven't had much of that - but I've tried it a little, and I want to get good at it because of the weight and packability advantage.
For the couple of times that I've tried it at low level, my conclusions were similar to
@sureshot. I learned that the size of the tree trunk is a limitation. Too big, and you can't wrap your leg or move the tethers up efficiently ... making the climb too difficult. When I have multiple tree choices at a particular hunting spot, I like to choose ones large enough that I can use the tree for a decent amount of cover when deer approach.
Many of the oak trees in my area are too big for 2TC. Since I'm hunting public land, I can't damage the trees, so screw in steps, bolts, and spikes aren't an option. That leaves steps with straps, sticks, DRT, or SRT. I like SRT for the larger trees, and sticks for medium-sized trees. If I can get up the learning curve for 2TC on medium sized trees, I'll probably never pack sticks again. Even so, I expect I'll still need to use SRT on trees with large trunks. So like sureshot, I'll be carrying SRT and 2TC equipment together, and use the best option for the tree I decide to hunt that day.