I assume with refresh rate you mean the fastest update rate of the GPS. I don't actually know for HTC Hero but as far as I know of this doesn't differ that much (could ask a friend of mine which has a hero but he's not available right now).
The HTC Dream (G1) has a update rate of about 1 second (it could be a bit faster or a bit slower but this will only be milliseconds). The HTC Magic (which I own myself
) also has an update rate of about 1 second (although I have heared people having update rates of 500 ms).
With kind regards,