I've had a A2Z CNC type QCTP on the lathe for about a year now and it's been a huge improvement over the stock tool post. However, I didn't like that it was made from aluminum nor that locking the tool holder in place pushed it away from the tool post itself, so only the two dovetails were in contact.
I happened across the Tormach 0XA QCTP on Little Machine Shop and immediately ordered one. Not only is it made of steel, but it's also an AXA or sliding wedge style tool post. In this design as the tool holder is locked to the post, it's pulled in against the post, so you have a lot more contact area between the two than with the A2Z CNC style; the 0XA is just a better design. I also really like that it comes with a knurling tool, which saves me an extra $25. Also, tool holders for it are cheaper than the A2Z CNC as well, which is nice since you'll want a lot of tool holders.
After installing it last night, I'm very impressed with it. The quality is excellent, and the added weight of the post and the holders is very evident. The back of the holders have a ground and polished finish. There's a very nice, tight fit between the post and holders.
Brand new the A2Z CNC QCTP costs $99 while the 0XA costs $129. However, in my opinion the 0XA is absolutely worth the extra $30, especially since you also get a knurling tool with it.