I got my shipment of these today. I ordered 2 of each because I wanted to try both styles, but felt I'd prefer the d-pad over the thumbstick. I started with the new d-pad and found that for my play style, the edges curve up too much and it was a bit uncomfortable. So I swapped in the thumbstick and I prefer it to the d-pad. Your mileage may vary, of course, but that's my first impressions after a quick gameplay session.
Regardless, both designs are a vast improvement over the stock d-pad. The increased throw in the design makes maneuvering much more precise. I've been playing a lot of Last Strike lately, which requires precise movements and found both designs were much better in that department. I want to try some other genres (fighers in particluar) to see how it holds up there, too.
Install was easy, just remove the four rubber pads on the back of the controller, unscrew the four screws under them and then there's one screw holding the top PCB in the controller. Take that out, pop out the stock d-pad, drop your new one in, screw it back together and you're good.
Here's some pics -- I am using them in repro Pro Controllers.