I used radicale but as gnome has owncloud support i switched to that some time ago. that hosts carddav and caldav and i don't use it for anything else.
gnome updates my contacts and calendar, but I use mutt as my email client... and i didn't find a way to access the gnome contacts from it. so, i also run pycarddav to be able to mail my contacts.
for calendar, the only one i like is california which is really fast.
Using both Ubuntu Gnome and Freya here on personal laptop and test laptop at work. Exchange support is available, though barely. I had to install Evolution and evolution-mapi for it to work with office 365 mail and calendar, but this is still limited to Evolution. Contacts works but not flawless. It syncs some contacts but not all and even for those that are synced, not all information are available. Sadly, you'll have to manually set it up on the Evolution client itself and not on the Online Accounts.
For standalone calendars on Ubuntu Gnome, I suggest installing California, a calendar app. I completely uninstalled Evolution from my Ubuntu Gnome desktop at home and replaced it with Geary and California. California is very similar to Maya so there shouldn't be much issue using one or the other..
what ?
EDIT: I guess you think I'm offering a replacement calendar for the one he wanted to install ?
https://wiki.gnome.org/Apps/California
I think California is gnome-calendar.... but I could be wrong, never used it. He will figure it out if he cares...