I've been SS'ing to work like that (geared bike sans derailleurs) for about a month or so now...it does feel faster to me. I think its something to do with the gearing I chose. I probably wouldn't spend more than 50% of my time in that gear if I had gears to shift...but since I don't have a choice, I ride the speed of that gear all the time.
I did notice a .5 mph increase in average speed on my cyclocomputer when I did the conversion too.
but man is it nice not having to fret over my derailleur once a week (usually at an inconvenient time) like I used to.