Every manufacturer has the occasional lemon and you tend to hear more about people's problems than when everything is working perfectly. That said, you can find plenty of reports of CZ providing absolutely fantastic customer service. I have 4 CZ's from the 75 series - a Pro-tek I, a Shadow custom, a 75B LE and a Phantom. The only problem any of them has ever had was I had the finish chip on the slide once. CZ refinished it for me without any questions asked. I haven't had a single malfunction though in any of these guns with thousands of rounds down range.
Ultimately it's your call if you end up writing the company off because of a bad report you read on this forum, but I'd also say it's your loss if you never own a CZ handgun. If you look, you can also find plenty of positive reviews of CZ firearms and CZ customer support.
As far as the P-07 design having a catastrophic flaw, I guess I just haven't seen evidence of that. There are tons of people who own these guns and they operate flawlessly. The earlier models did have some issues which they've now corrected and I've heard they are also changing the polymer they use in the frame to prevent the cosmetic bulge issues (starting next year I believe). If you had an errant piece of metal stuck in the extractor, that sounds like the source of your problems rather than some flaw in the design of the gun. That said, if you believe yours is simply a lemon and it's been sent back multiple times, I'd talk to their support department about possibly just swapping it out with another gun. Sometimes that's the easiest way to "fix" a gun with repeat problems.