If you are going to learn anything from this, Come Here Early!!
Gerstein has a great setup going and with the recent changes to the layout on the first floor it only gets better. The study tables and cubicles are spacious and brightly lit. Noise levels are beyond minimal in all of the areas and save for the winter months where pretty much every floor has a sniffer (I'm guilty of being one =P) its a great place if your study zen state is tranquility and silence.
I find that the main and 1st basement floors offer the best levels of natural light, which is by far the least straining ways to read IMO. The computer areas on the main floor are very comfortable, but also fill up quickly like the rest of the library.
The cafe is cramped and slightly stuffy so I'd say if you are willing to take a study break for food, make the trek to the med sci building cafe, which has much more space. It will be much louder than gerstein's cafe, but then again you're eating lunch so it shouldn't be too much of an issue.
Note: Wifi is "free", technically tuition pays for it.