I have somehow forgotten completely about ChangeTip, I used it frequently for a while and I probably still have balance there.

The two big things with ChangeTip is:

• one can very easily transfer money i.e. in a reddit discussion or in a github comment (more social networks are supported). I.e., I can tip someone for sending me a pull request, just by adding some few words to the comment I'm already writing while merging it. Time is valuable, management and micro management steals time, same with context switches. Switch the browser tab, and it's easy not to find the way back again.
• it's a nice way to push someone into the bitcoin economy; usually the receiver had the choice between receiving the tip in bitcoins or forget about it.