Rated 5 out of 5 stars

Excellent effort guys! Great extension that finally allows for using Microsoft Exchange with Thunderbird properly. However, I am still missing a feature that was already mentioned by other reviewers: the ability to see shared calendars of other users in my contacts. To be able to see when they are busy when scheduling a meeting is absolutely key feature. Is it really missing for now or am I missing something? For this I still need to use Outlook at the moment. Another wish feature would be to see the room list and its availability as well, though this is not as critical for me.

EDIT: Thank for your quick reply! You are right, free Free/Busy is indeed supported. All that was needed was a restart. I still didn't manage see the room list of my institution, but I'll investigate some more.

This review is for a previous version of the add-on (0.7.1.3). 

Thank you for the kind words.

If you just want to see when your participants of a meeting are free, you don't need shared calendars. Exchange has the Free/Busy feature which simply tells you whether that other person has a calendar entry at this time, or not, but not which appointment they have. Owl supports this Free/Busy feature. You can see it when you organize a meeting, after inviting participants to your meeting, and clicking on the button. You will see when each participant is free or busy. This normally even includes meeting rooms.

I hope this helps.