Nigel, i bought a 7D and took it on a 4 week family holiday, it worked astonishingly well everywhere from Hong Kong to Rome, and ol' London town, and in just about ll circumstances.
with the flash, just dont use it with a long lens, other wise the lens itself will cast a shadow, i have the 18-200, and at anything too far from 18, the flash was un-usable (i suppose this goes for all cameras though). The flash did work well, unfortunately all of the pics i have with it involve people who dont want their pics on the web (my family)
ive just included 8 pics to show the camera in low-light conditions, and a few others i threw in.
pics 1-4 + 6-7 were taken in at least ISO4000
John