Well I can't remember minding riding with studded tires in the past, but suddenly this winter it feels like a HUGE effort. Part of it is due to that I've gotten my first road bike and inherited a lighter mtb from my dh this year, so I'm spoiled with riding faster. The studded tires are on my old Trek 6000 commuter bike, which is significantly heavier than the other two even without the studs. But having two mtbs I can switch from studded bike to non-studded bike to bike with studs just in front in a matter of minutes in the morning - oh joy!

Studded tires weigh more and corner badly, but they can keep you biking blithely up hills you can't walk up. Just don't stop and get off, falling over and skidding down to the bottom is so embarrassing... I ride Nokian Extremes front and back, and they're held through more than 5 winters.

I find that when I drop below a certain speed I don't want to even try to ride faster, I just settle for grinding along slowly. Icebike has an excellent article on why winter riding is slower - I find it really noticeable commuting and doing the same stretch every day.
http://www.icebike.org/Articles/SlowerWinter.htm