Rated 4 out of 5 stars

I could set-up easily mail-accounts, which were on two different exchange boxes with different versions (10 and 13). The collaboration with lightning calendar and the Calendar EWS provider works also well. Both exchange accounts are large (> 8 GB) and have a lot folders. I feel the performance is reasonable, actually better for TB on linux than for OL on Windows 7 on the same hardware, although my linux sits on an external USB drive (which should be slower). Previous versions seemed to be less stable, but this one (24.5.2) seems to be mature. Given the value of an exchange account also for personal e-mail compared to IMAP for instance I think it is fair to ask for 10$/year; for corporate use it is anyway in most cases necessary to have a support organization available.
I know that there are some features missing; I don't miss them too hard, maybe only the ability to send S/MIME messages would be fine. Of the known issues the one with the two accounts on the same server is not nice; apparently a bug in the Thunderbiord core, however not nice.

This review is for a previous version of the add-on (24.5.2). 

Thanks for the review. I believe that I now have a workaround for the "two accounts on the same server" bug, which will be available in ExQuilla version 24.6 or later (available late November 2013)