
Need I say more? AutoISO on 40D actually knows just two values - 400 and 800 and in fact is unusable. 50D shows a HUGE improvement here and I would use AutoISO on 50D with no hesistation.
idk. i mean a single experience doesn't give the whole picture.
edit: read the part about the 40d manual stating that auto iso only works at 400-800.