For a commute like that I think tracking basic data is motivating.

I'd suggest:
-trip distance to hundredths of mile (i.e. 0.00)
-auto timer mode to only record moving time
-clock
-odometer
-ability to set wheel circumference to four digit accuracy

It will be hard to find one that doesn't also calculate and display average speed and records top speed, however these are less useful or can be calculated.

A backlite is nice, but not a must. I don't watch stats while riding, but only look after trip is over.

Al