I have a couple of hills on my commute. My normal SS gear is 74" [48x17 on 700x23C] on my converted mtn bike. Now that I have studded tires on, I am effectively at 77". Yes, I was too lazy to change my gearing.
Advantages - I'm only a little slower than I was on slicks, mostly because I can't spin the heavier tires quite as fast. Torque is reduced dramatically, so I don't lose traction on climbs.
Disadvantages - At some point I'll do the Walk of Shame, because I won't be able to push that gear through 6" of wet snow.

Last year, I rode a different mtn bike all winter with 26x2.1" studded tires. The gear was a 42x16, so around 68". It got me through everything except for the heaviest snowfalls.