I'd really like them, but I would want them to have the ability to override regardless of where the stick is.
In the VW vehicles, you can have the stick in Drive, Sport or the tiptronic slot. Pressing on the paddle shifter will drop / climb a gear immediately. It works very well too. After a period of time, it will revert to the previous setting of Drive / Sport / Tiptronic.
I hope Volvo do bring this out at some point, and somehow make it a retrofit option for Geartronic and Powershift models.
It's the Ford system I am told, and it's been going strong for about 3 years now. The initial problems with shifting were ironed out in the Focus, it's had a few software updates over the pre-Volvo time. They reckon its all sorted and good for use now.
I find it shifts almost perfectly in sync with where I would have manually shifted. In sport mode it hold the gears longer, turns off auto-stop and really makes the car a lot more responsive to the throttle.
Tonight I had it in sport, I was given a gap in a long stream of traffic to go through, at which point another car came around the side of the stopped car and we came within inches of each other. The V40 went where I needed it to go, I felt totally in control all the time. Had we come together it totally woulda been my fault, kudo's to the other driver for taking avoiding action as well. I would have been heart broken if I had scratched my V40.