Tire weight and rolling resistance do make a big difference. If you want a quicker riding commuter, Continental has some good choices. I've got Conti GP 4 Season 28s on one of my commuter bikes and it is everything you could want in a tire -- durable, light weight, flat resistant, low rolling resistance and nice handling. They are a little more expensive than Gatorskins but lighter and grippier in rain. They are available in 23s, 25s and 28s. For commuting, I would get get 25s or 28s, but make sure your frame has clearance for the larger sizes. I also have commuted extensively on Conti GP 4000 25s with excellent results as well but they are not available in 28s.

There are lots of options for durable, flat resistant commuter tires but not many that are also light weight, nice handling and low rolling resistance.