Was down at the humber today doing some Outdoor Ed with school kids. Took an ax with us for firewood, but we used it to chop a hole in the ice and set a homemade minnow trap (didn't catch anything). It's a good ten inches of solid clear ice under a foot or so of layers of slush and thinner ice (from the recent thaw and re-freeze). Right under the Bloor St. bridge you can see how thick the ice was from the early season (January) ice dams.
That being said if it gets up to 10 degrees on wednesday like it's supposed to, there'll definitely be some major break up just as Blair said.
Also worth noting, the mouth of the river is open south of the Gardener, with the warm weather, this week could be a good time to chuck some spoons for rainbows and even pike.