Using python poclbm-mod.py -d 0 -f 0 -a 10 -v -l, I regularly see between 21230 and 21255 khash/s. I've also noticed that -v (vectors) costs about 300 khash/s (21567 to 21579), but I think there was an increase of invalid/stale shares --- this may have been due to other factors, however. I also think there was a reduction in discovering multiple shares per getwork without vectors, but that may have been due to the same 'other factors'.
I don't know what the wattage draw is, but I have noticed the temperature of the card jump from 58 (idle) to 72 (mining). I'm guessing these values are in fahrenheit.
If they were in farenheit, youd have the coldest GT 240 on air lol.... mine is that - 5~6 degrees Celsius because I redid the thermal paste