Lennar's no-questions-asked, no-SSN labor installed HVAC vents five feet off the floor, put a security keypad directly on top of a light switch, couldn't get the counter/cabinet assembly plumb, and botched nearly every corner's molding (at ceilings) or quarter-round (on floors). We got lucky and managed to get them to fix most of those.
Of course, that was BEFORE they got our money. Three windows were installed off of square and cracked from the strain; they refused to fix them, saying it could have been something hitting them, despite the fact that all three cracks began in corners and extended inward. A crack opened up in the counter - after the warranty expired, of course - at which time we found that rather than re-doing the cabinet/countertop, they had just wedged some shims between it and the wall.
Ten months after we moved in, the rainy season here in south Texas began and we learned that a huge patch of our back yard turns into a mosquito breeding pool because of improper drainage. After we called them repeatedly, they came out, dug, put in a few square yards of sod, and told my wife she had to sign off on the work order before they could finish. She did, and we never saw them again. They now refuse to do anything, saying that they've completed the repair.
A few months after we bought the house, we found a leak in the garage. This started out well - they sent somebody out who fixed the leak and cut out and replaced the damaged wall. Unfortunately, "fixing" the leak involved smearing caulk or something on it and hoping it held. We found water damage in exactly the same spot last month, and I went up to the roof and found out that the ridiculous repair job had failed; the caulking had cracked and the leak had opened up again. They're refusing to fix it because it is now out of warranty - apparently, if they pretend to fix it once, they never want to hear about it again.
The guy who deals with this stuff is condescending and rude, and takes three days to even acknowledge communication. I'm done trying to deal with him. If I can't find somebody at the company who will actually take responsibility for their work, we'll see what the BBB and Texas Residential Construction Commission have to say.