Well, I'll chime in with my $0.02...

I tried Strava, and I will agree that it is good at what it does, and the social aspect is pretty appealing, but I chose Endomondo. It certainly doesn't have the following that Strava does, but it does everything that Strava does, and the Premium version (for ~$4) offers some pretty cool features.

1. It allows you to create your own interval workouts and use them for training.
2. You can compete against your past PR in real time.
3. The app integrates the phone's music app for those who want to listen to music while you ride.

I've been using it for a while and it's pretty cool. Give the free version a shot; you might like it. I'd sure like it if more people started using it.