I registered for this forum to post with this thread. I was following it for a while before I bought my Mag, and was aprehensive before buying one, but so far I've had it for 2 weeks working fine.
I DID have problems with it out of the box. The first day I had the tv, it locked up when it lost VGA signal, occasionally locked up when selecting input source, and it wouldn't hold scanned channels. (Using Cox cable, btw)
I went to the factory menu by hitting channel up+volume up, and selected "factory reset" under the advanced menu. After the tv powered back on, it now scans and holds channels fine, and I have been unable to cause it to lockup with any amount of screwing around with the inputs. Sound is also fine after making the recommended adjustments found earlier in this thread. I've got cable running into the coax, ps2 on component, dvd player on s-video, n64 on rca, and xbox360 on vga connected to it with no problems.
I'd suspect there's some sort of faulty channels preprogrammed into it that the factory reset can clear out. Prior to doing that, everytime it lost its channels or locked up, it would come back with the same two channels (3 & 7) and the same predefined menu settings. Still seems kinda odd that it had those problems, but the reset seems to have fixed this for me, and I'd recommend the tv as long as you're willing to take ~5 min to do this out of the box.