Orchard Restaurant is pretty much THE place to go in Mississauga for breakfast. Even if you don't like it, you've probably been to it at least once - it's the landmark at the corner of "Five and Ten" (Hurontario and Dundas). Anybody who's anybody eats here. Mayor Hazel McCallion has made it a regular stop. I've had committee meetings and social get-togethers here. It's almost like a rite of passage if you're a local resident.
Of course, it sticks out like a sore thumb because of its retro decor, but the food has always kept me coming back. While the prices can err a bit on the pricey side for bigger breakfast items, the food is always delicious and you get generous portions. Whenever I go, I usually get the "Mississauga Platter" (which is basically eggs and all the fixings) or the "Cluck Cluck Benedict" (eggs benedict with a chicken breast), which always makes me laugh when I order it.
The menu is by-and-large the standard diner fare, and the staff are reasonably courteous given the high volume of people who come through (just don't look at the cooks behind the grill - they look like they'd rather be somewhere else).
Orchard is a place you go more for the experience than anything else. It's consistent enough in quality to recommend, though I'd stick to the breakfast hours and avoid the loud screaming kids with their parents at dinner service.