I recently replaced an arch linux installation with debian jessie; after
installing gnome, I noticed that ram usage was a bit higher than I was
accustomed to.  The biggest difference seemed to be the overhead from
evolution-data-server, which is pretty high.

This package is optional on arch, so I rebuilt the .deb with moving this to
a Recommends: dep; after removing e-d-s, ram (and quite a few packages!)
dropped away.  The functionality that goes away is mostly related to
calender events (and making clock pop-up more complex).

The related arch linux bug:
https://bugs.archlinux.org/task/37927