It is just another Starbucks. The only difference I have noticed is the size an a few more couches for people to sit on, plus the more Victorian/library vibe and decour found inside than in other locations.
As par of a chain, this place is no different as far as the food/coffee is considered. Personally I have been there a few times, but every time I have meant to hang around/chill/loiter our plans have been spoiled by the large amount of customers who seem to live here.
One or two homeless people who are regulars will stand outside to pester you for change.
As far as convenience, this site is seconds away from the West exist of Yonge and Bloor, so if you are in a rush, you can easily sneak out of the TTC, get a coffee and get back in without fuzz.