I have to say that (personal feeling only) they are improving. There was a point where I was close to dropping Ubuntu. Now I notice that many of the most annoying bugs which make it into releases are at least getting fixed within the first two to three months (previously they were simply never fixed). A small improvement, but enough for me to wait a bit to see what else improves. As mentioned above, if they were to move to vanilla kernels entirely instead of brewing their own thing (in fact if they were to brew their own thing a bit less generally - apparently they are finally dropping usplash and will use Fedora's one instead) they might also have more resources free to squash bugs. Hopefully this article indicates a step in that direction.