What is a safe CPU speed for the HTC Dream?

I know that T-Mobile clocked it down to 384 to extend battery life on the G1, and I believe that the processor was designed for 528. With all that said, does anyone have experience with what a good, safe speed is? I'm new to Android (less than 1 week), so all this is new to me. Thanks! Update: the processor is the MSM7201A.