Before you start to feel bad about your own personal slow speed, when reading posts about commute time or max speed, you should first consider the exageration factor that is commonly added to many (but not all) of the posted numbers.

My commute is all hilly, but nothing extremely steep. Today I got up to 28 mph (=33.7 mph with exageration factor) on the biggest hill with my fixed gear with 70.2 gear inches. I can go a little faster if I try real hard, but my cadence abilities top out around 30. I have no idea what cadence that is, but it feels pretty intense, especially after having just climbed the other side. On my geared road bike I can get up to 32–35 (= 41.2mph with exageration factor) going down that same hill. I try to make it a point of hiting 30mph at least once a day.
There is a tremendous hill (not on my commute) along the Hudson river just North of NYC that I used to ride down full blast on a geared bike, blowing by other cyclists who were not a stupid as me..total daredevil stuff. I want to try it again now that I have a computer just to see how fast that really was, but I don't think I have the nerve to blast down it again.