From What I hear... the older ones had some issues with the frame being too soft and a spring causing a bulge.
New ones have fixed this problem by using stiffer polymer, but some of the older ones are still lurking unsold. If you get one, CZ will usually replace it for a newer one.
Most on this forum have high opinions of the P-07.
The 9mm may be more likely to be 100% reliable than the .40, but that is speculation. There are a few instances of lemon P-07s out there, but CZ repaired/replaced the pistol and the person was satisfied. Any gun model will have a small percentage of defects in a production lot... its when a model has a very high rate of lemons that you should be wary. I have not seen that with the P-07 from my research.
The biggest major defects I have seen have been a few cases of a broken spring that caused the pistol to stop functioning.
The rest have been FTF that are either ammo related, or pretty easy to fix with a good polishing of the breech face, extractor, and feed ramp. (maybe an hour's work using a dremel polishing wheel) Or let CZUSA do the work under warranty.
All the problem guns have shown up in the first few hundred rounds. (500 or so) So if you get one, start putting rounds through it and see how it does. If you can get through 500 rounds with no problems then you are probably good to go.
I have two CZ 75Bs but not a P-07... I have had one FTF in my .40 and a quick polishing sorted that out. The 9mm has been flawless so far.