We flew GOL from FLN to GRU a year or so back. Quick flight, on time, no problems. Transit in GRU is quick. And, GRU is not a great airport; the less time spent there the better. As for the FLN-GRU route, in the summer a number of Sao Paulo businessmen "commute" from FLN to GRU on the weekends, leaving their family to enjoy FLN during the week.

Floripa is great. Make sure you take the drive to Ostradamus for a seafood lunch. Just terrific.