Most Significant Changes from 2.0.x to 2.2.x ?

I've got a store running on 2.0.15 with fairly heavy code mods but they are all commented well. Need to summarize for the guy who writes the checks for development what the big improvements are from 2.0.x to 2.2.x. Without going through all the version release notes, can people throw me a bone a chime in what you consider to be the most significant/worthwhile improvements that have been made?