Sorry, Loupey, I wasn't very clear. In addition to testing hand-held (IS on) and tripod (IS off) at the same settings, I tested the same way at two different ISO settings to check for noise (which also affects clarity) between the hand-held and tripod shots taken at 100 and 800 ISO--not at the same ISO.
I'm pretty steady off-hand, but I doubt I'm as steady as even a cheap tripod, so I came away from this very confident in my Pentax's in-camera IS.