I really don't understand the round trip talk with commuting. You ride 30-40km, cleanup, work/rest, then ride home 30-40km. To me, once I'm spinning... the miles seem to mesh together. I really have trouble guessing distance and many times I've thought I've only ridden 10 miles and turns out someone with computer says we've ridden 20+ miles. To me, commuting is all about time and how long it takes you to get there given the effort put in. There are so many variables to this that no one can answer. Gearing, traffic, road conditions, weather, number of intersections, etc make it impossible to really compare with you.

FWIW I commuted for a year on geared bike and then 150 days on a fixed gear bike. Commute was 10 miles one way with 500ft of climbing. I enjoyed it so much better than geared as I didn't have to worry about anything on the bike except for tire pressure. I enjoyed the lighter overall weight and the low speed control (waiting for traffic or redlight). I plan on doing 12 mile commute to school (different attire) in September however I'm thinking about giving SS a try.