Winter commuting is about safety more than speed, so true. Relax and enjoy the ride. And studs are great training! Think about the benefits of your extended saddle time, remember that you're keeping your summer fitness up, maybe even improving on it, and don't worry too much about speed. Plus, you are reducing your risk of an injury that would keep you off the bike completely.

I have Nokian Extremes on a very heavy mountain bike, and it can feel pretty slow at times compared to summer (although you do get used to that after a few weeks, and get the reverse feeling for a few weeks in spring with the rush of easy speed). However, my winter cruising speed is about 25 km/h (15 mph), so I'm still a relatively fast cyclist even with the studs, and it's all the sweeter when I know the guy getting passed can hear the velcro-like sound of my studs coming for him... oooh and then the salt in the wound as I say hi and go by; I'm a girl! If I was riding a road bike, the bike would get to take all the credit.