He used to get one for all his cars when he was sponsored for stereo stuff (couple different cars too). Never once did he have the slightest hint of a problem. So I based my opinion off my/our experience with them. Then I read the whole miata ordeal, which turns out I either imagined it all or didn't search back far enough to prove I wasn't crazy. I know I saw a few other friends with them that didn't have the best of luck, but not enough to really pass judgment on. Then I started seeing more and more in person that were bad. But finding lots of negative posts on them seems to be somewhat difficult, or at least was when I checked due to my conversation with whomever it is a few months ago.
That being said, I wouldn't buy an Optima if I had no choice.