I recently started using Evolution as email client instead of Mozilla which has been my favorite for the past few years. The main reason would be the calendar feature.
There are 2 things I've noticed and not like:
1- it's kind of slow when I switch from one folder to another
2- and the major issue is the "Edit As New" feature that Mozilla's got. There is a way to have this feature available but only for messages from the "Sent" folder. I have not found any other easier way.