This is the first result that comes up for Harvey's so I'll just use it as a general overview of the chain itself. As the first poster notes, there seems to have been a pull out of the chain in certain areas of downtown. There's one in the bowels of the Eaton Centre's food court (the southern wing) although it's tucked around a corner and you have to get by the stank of the Sbarro to find it. Even if'in' you find the Harvey's there well good luck finding seating in the foodcourt area. Your better Harvey's play is kitty corner at the AMC Dundas 24 building on the foodcourt level (which appears to double as Ryerson's east wing cafeteria).
There is also one in one of the food courts in the financial district underground but I think it's only open Monday - Friday 11:45 am - 1:45 pm so forget about it.
Right. What is Harvey's? Well, it's one of the few burger chains that manage to match your mom 'n' pop stand alones that engender local loyalty (i.e., Etobicoke's Apache Burger). It's a bit like the American West coast's In 'n' Out burger or Seattle's Dicks.
Harvey's offers a flame broiled "meat" patty (not 100% beef as far as I can tell) made to order. You get to load the sucker up Subway sandwich style. They seem to have a policy to cater to "extra" and "on the side" requests with little complaint. Pickles on the side is usually a favorite request of some. I personally always ask for four scoops of onions and have never been turned down. (I do allay the food prep's fears about the societal consequences of eating so many onions by pointing out I'm single and won't be tormenting anyone with onion breath. I also have a theory that the extra onions contain sufficient cancer fighting enzymes that counter balance the carcinogens in the meat. But don't construe that as Kevin Trudeau style "health" advice.)
Harvey's sometimes follows the "if it's not broken, we're going to try and fix it" school of driving a good brand name into the toilet. Harvey's, for years, had some of the best fries around: a fresh cut potato fry with just the right amount of potato skin and crispiness. In the late 1990s/early 2000s they changed to this coated "seasoned" fries which were just awful. Awful. So awful I think I actually wrote my MP and the Queen a letter asking them if they could do something. A truly "New Coke" move. They seem to have brought something like the old fries back but not quite.
Harvey's should not be confused with Hardee's. The similarity in names actually prevented the Hardee's chain from expanding into Canada. So if you dream about tasting a Monster Thick Burger, you'll have to keep on dreaming.
All 'n' all, Harvey's has made some changes over the years in the "not for the better" category but it's still miles (errr kilometers) ahead of McDonald's and BK.