I've been building systems since years before AMD made GPUs (and before that, ATI) and nVidia was building viable GPUs. They're both similar and their products generally work without issue. I care not to count how many cards I've owned (and money I've spent) from both companies over the years. AMD has had a few blips on the driver front, but for the past 5-6 years they've been solid. I generally have no qualms going with either, and am led by pricing and rasterization performance above all.
I have seen way more shenanigans from nVidia where they really push the envelope of what's morally (and sometimes legally) acceptable e.g. 970 "3.5GB", impeding mobile overclocking, continual and insidious methods to push pricing ever higher, banning reviewers who don't follow script. I could spend the next hour listing examples... They're really shady which has generally pushed me towards AMD of late, all things being equal. Not to say AMD doesn't have their fair share of anti-consumer incidents (ahem, completely dropping driver support for "mobility" chips when it didn't suit them, pressuring ), but they been generally more kosher in this respect, possibly due to having for so long not been in a position of power they could abuse.