My 0,02€: get a decent pair of panniers. You probably have rain in the summer as well; buy a bike with fenders and lights. With the downtown traffic all your bike gear should preferrably be very visible, with lots of reflectors and bright colors. And be prepared for the exercise at first, 15-20kms one way will take its toll.

After a season of summer commuting get ready to browse the net and Forums for studded tyres and other winter gear!

--J