I just did a fresh install of 12.1 (I was using 11.4). I had some issues with the install, that being that it crashed once while installing, and it crashed 3 times when it was auto rebooting after all files had been transferred. I saw that it said it was trying to reset without an actual full system reset, it appeared to be hanging at this point and then the display would flicker and then lock with a random pattern on the screen. If I manually turned the machine off and on, I was able to continue the install though it did give the message that install failed.
One of the other issues I had was (and one of the reasons I had to install several times) the installer did not appear to be writing the MBR properly. When the boot menu would come up, it had an option for 11.4 on it, and the option for 12.1 would not boot. It would show the message of what image was being booted and never go past that. The drive that had the old MBR on it was detached (since I knew it would probably cause issues like this), but there was one drive that had a copy of the root directory from an old system. It was, however, not the first drive, and it was not to be automatically mounted. Either way removing this drive allowed the machine to boot normally (no new install required).
Now the the machine is up and running, there are a couple issues I have had. One is that while copying the files from my backup of my home directory (using the copy/paste method), I locked the screen and when I came back I found that the copying had stopped and would not resume. Now I cannot copy and paste anything file system wise (copy and paste of text works still). The other issue I have is with my audio. When I used 11.4, my audio was very balanced between high and low frequencies and I could use the volume control on my bass to adjust the level of bass (so when I turned it all the way up there was a lot of bass). There is hardly any low range now even with the bass volume turned all the way up, even when listening to very bass heavy music.
Any help is appreciated, my system config is as follows:
Asus M4A89GTD PRO mobo, AMD Phenom XII 965 black edition, 4gb Ram, Nvidia GTX260 graphics card. Western Digital Caviar Black 640gb sata6.0 main drive (other drives are not attached all the time)