I also have the 512 x 2 version. It's been ten months and no memory related failures, I haven't done much as far as pushing it much past 800Mhz, but I have read good results on the newegg reviews, such as over 900Mhz.
My MB defaulted the RAM to something like 1.8 or 1.9v and I was having a lot of issues, once this was discovered I bumped it up to Patriots spec which is 2.2v, been fine since.
My last pair of 512 DDR1 sticks in my last computer ran great for many years. I like Patriot and will be buying from them again.