I've used Hitch regularly over the past few months, and it works well for short trips. Half the time I don't carpool (and I still pay half price), and the other half of the time adds just a couple extra minutes (haven't gone more than 5 minutes out of my way). My one issue with Hitch so far is that occasionally it takes a while to get me a ride. Uber has a leg up here, as it has a huge scale advantage. When I open my app, I can see 5 ubers in a 3 block radius - which is pretty astounding reach.