I got a bike just for commuting on last year and I had a few must haves:
Disk brakes save wear and tear on over rim brakes and are more tolerant of bashed wheels.
Robust tyres with a reflective band, currently using 32s, not yet felt the need for slime filled tubes or additional protective inserts. The solid tyres have caught my eye too, maybe one day.
Cheap groupset as I do not want to be too precious about wear and tear, Claris does all I need. 50/34 and a 12-25 is ideal for me.
Fit mudguards year round.
A nice colour, for admiring - very important.