I'm with Wally on this one. I always keep rope readily available and have occasionally just tied it to the handle when I need it but the need is exceptionally rare. Most of the time I want my canoe out of the water when I'm not in it. I wet foot and when I get to shore I pull everything out, put it on shore, then either carry the canoe across the portage or put it next ot the gear, depending on circumstances. It always ends up bugging me on portages when I carry someone elses canoe that has a painter because it always seems to get in the way somehow, though I guess tieing it down better would eliminate that most of the time.
I also agree with whoever it was that mentioned wanting the canoe to slice cleanly through the water. It seems to me, you start getting too close to the water line and you're going to, at least occasionally, be dragging that rope through the water.
All in all, I think a painter is pretty unneccessary regardless of how it's attatched.