When I first considered commuting with a fixed gear, I did as krusty advised.

I did my ride on my geared bike, but in only one gear.

As for hills and fixed gear bikes, we have a hill here in Bend that even geared bike commuters dread.

At first, I thought I would die on that hill, either from a heart attack or from my lungs turning inside out and coming out my mouth.

Now I do it in the saddle and wonder why I ever feared it.

As for gearing, last year I geared way down to 60 gear inches (39 X 17) so that I could continue to ride through chemotherapy, and my spin improved so much that I now commute as fast at 60 gear inches as I ever did at higher gear inches.

Commute fixed and you'll never go back to geared.