I don't have a favorite hotel for hobbying per se, but over the years, I have stayed at a number of hotels in the downtown core, so I offer up a few observations.
My most frequent hotels used are the Sheraton on Queen, followed by the nearby Hilton. I like the Sheraton because of its location, its access to the underground tunnels (very useful during the winter), and what seems to be a very sp friendly environment. The lobby always seems to be busy, so there is never any reason for an sp to feel self-conscious. I like the Hilton too, for similar reasons, although I prefer the decor and appreciate that there are mini-bars in all of the rooms (at the Sheraton you only get a mini-bar on the Club level). The only downside of the Hilton is they will intercept people walking into the hotel after 11pm. Usually all they do is call you and confirm you are expecting a visitor. It is not a huge deal, but a slight hassle.
I have stayed at the Inter-Continental on Bloor a couple of times. Again, great location, very nice rooms, and never any hassles. Ditto for the Marriott on Bloor near Bay. The rooms in this Marriott are usually very good sized with interesting configurations, the only drawback being no mini-bar. The Marriott Courtyard on Yonge is a place I've stayed only when I wanted a cheapo rate via Priceline. The rooms there are kind of blah, but there is free internet, and again, no sp hassles.
Every now and then, I will stay in the Dundas/Jarvis area, either at the Grand or Comfort Suites. The rooms at the Grand are quite nice, and usually there is a very conveniently placed mirror by the bed which appeals to the voyeur in me. At the Comfort Suites, I always reserve the two room suite with jacuzzi. It is nice having a separate living room and kitchenette, and the jacuzzi is wonderful for sp action. Only downside is the location, which isn't the ritziest.
Finally, I like the Pantages on Victoria near the Eaton Centre. The rooms are very nice, beautifully furnished and good sized, with a kitchenette and even a washer and dryer. The big downside about this place is that the elevators require a room key to operate, so therefore you have to go down to the lobby to meet your guest.