Couldn't find this posted before, but in the Elite Connection summer edition this is mentioned:
Connecting to the U.S. is easier via Toronto Pearson
As of June 30, 2011, the U.S. customs process at Toronto Pearson Airport will be much simpler. You will no longer need to recheck your bags. Just scan your boarding pass at the kiosk and you're ready for customs!
Is this similar to YVR? I'm actually on YVR YYZ DTW this June 30th so it'll be interesting to see if I have to recheck my bags or not.
Can't find anything re: this on the YYZ web site.