I work in the south end of campus, so I don't go here very often, but every time I do, I usually turn away and head to the one on College & Beverley. The time it takes for this lineup to reach the front will be as long as it takes for you to take the extra walk.
As an industrial engineer, it really irks me that they have ONE barista serving the endless lineup at Robarts, the largest and most central library on campus. They should consider all of the revenue they're losing to other locations.
If you don't want to cross the street, there's also one in the CCBR.
Both Starbucks locations accept the gift card. The U of T locations that don't are the Aramark cafes that serve Starbucks coffee. Don't EVER go to those locations. They don't even give you free refills.