I’ve tried geary in the very recent past and although it’s very nice, it just can’t compare to the competition.
Evolution is far superior in every possible way, integrates with GOA and also has calendaring, which is paramount for work. Other than no CSD, it looks and feels right in Gnome and Unity. And I believe some of its backend components are already in use by the DE.
Thunderbird is also up there with Evolution, but it does not integrate with GOA and has trouble with local storage: connecting it to my 15 year old GMail makes it use around 10GB worth of cached storage.