As much as I like the CZs I own, I consider all of them to have been projects that I wasn't happy with out of the box - esp. when it came to triggers. As others have said, it may not take that much to improve them, but unless you are buying a Shadow, they generally can all stand some degree of upgrade.
In comparison to another very well-known make of DA/SA pistols, I'll just say that you may pay more for that other brand, but they typically need little, if any improvement, out of the box. I think a lot of it comes down to - do you want a pistol that's ready to go? Or do you want to save a little money up front, and then spend it on improvements? There are solid arguments to be made either way.