I integrated the hashmeter idea into the SVN version.  It displays khash/s in the left section of the status bar.

Two new log messages:
21/06/2010 01:23 hashmeter   2 CPUs    799 khash/s
21/06/2010 01:23 generated 50.00

grep your debug.log for "generated" to see what you've generated, and grep for "hashmeter" to see the performance.  On windows, use:
 findstr "hashmeter generated" "%appdata%\bitcoin\debug.log"

I have the hashmeter messages once an hour.  How often do you think it should be?