This is a Very Good Thing. When I had the first ultrasound in July 2005, there were tons of the buggers. Even I could see them with no training whatsoever - they appeared on the mostly black & white ultrasound picture as coloured spheroids which sparkled & "spangled" as I moved around. There was also lots of "sludge", which is mostly what was causing me pain.
So the gallstone-dissolving medication is working, and no new gallstones have formed. Hooray!
This does not, of course, guarantee that my gall bladder won't spontaneously start producing more stones in a year, 5 years or 10 years - but it means I'm ok for now :)