Backerkit - what is your experience with them? Horror stories? Recommendations?

If I ever do another Kickstarter, I am thinking of finding someone other than me to mail out the rewards. I have never backed any projects that used Backerkit, so I am now wondering what these services are like?

Have you backed anything that has used Backerkit or a similar service to send out the rewards? What was your experience?

Have you used these services as a Kickstarter creator? Are they easy to deal with?