I guess the point is that yeah, there are bound to be errors in a game like Dwarf Fortress. For the most part they disappear into the background though.
I'm probably going to regret posting this so I'll start with the disclaimer than I love the game, I recommend it to everyone who will listen (and bore those that don't) and I donate to it.
With that said I have to comment that the bugs, for me at least, isn't the major problem with the game. Technically the new 3D version of the game is infinitely superior to the old 2D version, you can do more stuff, have much higher ability to design elaborate ways to have Fun and so on, but honestly I have to say I miss the old version it had something the current one doesn't and in a hard to describe way is a better 'game'.
However this isn't a game for me, and I don't expect Toady to design for what I prefer, it's his game and I've only donated because I want to it's not like I'm buying it and expect support. The dev log, to me at least, looks like it will eventually return towards what made the 2D version so much more enjoyable and I'm so I'll wait. There is also a good chance if I went back and played the 2D version I would miss the features of the current one.
With regards to bugs there are quiet a few things you could class as a bug but I've also yet to come across a fatal one. Lots of annoyances like being unable to dump claimed clothing that is then left laying around, or dwarves dodging off cliffs when they have wide plateaus to the other side of them. There have also been a couple of bugs that kept popping up which to my mind is the sign of bad development process, but that is something that improves with time.
As to cyclomatic complexity it's a common and well known concept but not relevant in my mind. Your modules of code should never get so large that they hit any problems with complexity, if they do you are not correctly breaking the modules down. In studies it has been shown that bugs rise in colleration with the cyclomatic complexity of any discrete modules, the same is not true of the total program though.
As a final disclaimer the above is based on my experience with development and in no way should be taken as gospel or used to attempt to prove anything at all