Welland Canal going downhill is quite easy. Uphill is quite a bit tougher because of the rush of water into the locks. If the weather is really hot you might want to do the transit at night. It is fully lit and you won't get baked in the locks.
Sorry for the bum steer about the Trent. I have not sailed on the Great Lakes for several years and forgot about the low water levels.
Back in the water in Grenada - with new main and #2 and cockpit canvas (Santa came early). Will spend the winter and early spring in the Caribbean and then head to Bermuda and the northeast US. Still trying to decide if we will bring the boat to Canada, either in 2015 or 2016.