My commute is very mixed as I live in the country but only 12 miles from an extremely busy international airport and 15 miles from work.
Mornings are magic, dark or light doesn't really worry me either way as at 6am it's just me and the local wildlife for the first 6 miles.
From there it does kinda start to go downhill as I venture through a few busy towns with busy roundabouts and a short stretch of dodgy dual carriageway, before tackling the last couple of miles that I've never liked, not entirely sure why although it does feel like it's always in a headwind no matter which way you are going and a poor soul on a bike was killed there a couple of months ago.
Evenings are a different kettle of fish altogether though. It turns into a battle for position almost immediately and you need to keep your wits about you almost all the way home with one of the worst bits going past Dykebar hospital when all the cars I've passed all the way back from Renfrew, finally start to pass me and it can sometimes feel like one long continual punishment pass.
I do enjoy my commute but I would change the traffic at times.