I use distance, speed, average speed and cadence (though not cadence on the fixed gear).
Why?
I'm a numbers nerd and like recording and looking at them. They serve very little use beyond that though occasionally it's been useful to look back through the log to work out how long a trip is going to take me... and that's been very rare.

I have found that it's too easy and a big mistake to let the computer dictate how you ride - trying to maintain a cadence, trying to maintain a speed, trying to maintain an average. This is a mistake because you will push yourself too hard... though that's not always a bad thing in itself.

I ride for pleasure. I get my pleasure in a particular way. You might get pleasure from different things to me (eg, smashing yourself to beat a time). However, if you're not enjoying, you need a bloody good reason because I can't see the point.