We stayed at the Hilton Suites in Markham last year, and liked it and had no problems. This year we have booked to stay at the Sheraton Toronto Centre, at the end of August. First time using Hotwire, and got the Sheraton for $66,night. It looks nice, and close enough to everything. Parking seems expensive, but you would have to pay it regardless.
The Hilton, you also have to pay for parking, but if you get a deal where it includes breakfast then it is worth it. The breakfast was very good.