Next to the Reference Library, this is my favourite branch of the Toronto Public Library - mostly thanks to the wicked awesome building it's situated in.
Because it's a bit of an older building there's nothing particularly flash about this particular branch, but I think it's got quite a character of its own, especially with the odd round reading room on the south side of the building.
Services are decent (they have a small bank of computers), there's a reasonable selection of stuff on shelves and they are a reasonable location to grab holds from. There's a bit of bottlenecking near the stairs/entrance if there's a bit of a lineup, but most of the rest of the building you won't find hard to get around. Unlike the Ref. Library - and despite the building's awesomeness - I generally don't aim to spend time here; just get my books and scoot.
A short walk from bus/streetcar stops and St Clair West station makes this ideally situated. If it were open 7 days a week, I think I could squeeze in an extra star.
[They do get bonus points for appearing in the Scott Pilgrim comics *and* movie though.]