currently I have 4 sets of DDR2, and I have tried 1T on 3 of the 4 sets, and have had great luck breaking 1 Ghz with all 3.
the best set, I can do cas 5-4-4-10-1T at 2.55 volts and 1100 MHz.
I tried to duplicate the persons OC who posted cas 5-6-6 at 1200 mhz and 1T, and while I can get it to boot every time at that speed, I cannot make it into windows ever.
so atleast I know 1200 mhz, at 1T is possible on this board, if you have some great ram.
while I believe I have great ram here, I couldnt do 1200 mhz stable at 1T myself. but it does boot, which tells me it is indeed possible.
1100 mhz, at 1T is my best so far.