I've been going to The Rosedale Diner for years now and I've always had a great time. The atmosphere is always very pleasant and the service has been great. The owner is sometimes there when I go, and I think it's a nice touch when the owner of a restaurant checks on tables. But, yes, as others have mentioned, the service is relaxed, but I've never felt it was rude.
The food is delicious, especially the the Poutines, Duck Confit, Sesame Crusted Chicken Sandwich and I've had a sirloin there that was amazing! Also, they've recently had Wagyu burgers on the specials menu and they were fantastic!
I think my real attraction to this place is the summer patio. They serve lattes in lovely handmade clay bowls under a tree canopy, and it's simply stunning. Although, word of cation: the chairs on the patio are far to low to the ground, so tall people beware!
All in all, I take people there all the time and 9/10 people enjoy it immensely. It's worth heading north of Bloor for!