I use Strava on my commutes. Since my phone's coming with me anyway I find it not cumbersome at all. While I have successfully tracked century rides with my phone, I recently picked up a bike computer for longer rides. I don't want to end up in a position where I need to make a call at mile 80+ or lost & need to start using Google maps with a phone charge under 20%.

I aslo like using it as an odometer for my bikes, as well as a ride log book. It's helpful for tracking maintenance, seeing trends in ride time, effort, etc. The auto post to Facebook is convenient as it's one less step to do in order to let family know I wasn't in an accident and arrived at my destination.