This is a pretty typical greasy spoon serving your standard breakfast options at a reasonable price.
There are a couple of others like this in the area (Good Bite is one) and of all of them, Mars Uptown is my favourite. I find the food here the best (not insanely greasy, great omelettes), the seating to be the most comfortable, and they do the best job of making sure my 'bottomless' coffee cup is always full.
It does get very busy on weekends (as you'd expect).
The front display case where they show their muffins the last time we were there was disgusting (crumbs everywhere). Hopefully not an indication of what goes on in the kitchen.
I'm not going to HIGHLY recommend this place because there's nothing outstanding about it but it is exactly what you'd expect from a greasy spoon and the best of it's kind in the Yonge & Eg area.
*Tip: Don't order a soft drink...apparently they come in the smallest bottles you've ever seen**