Rated 3 out of 5 stars

After the developers hint to disable Birthdays Calendar it is quicker, but still does not perform like it used to. I think this is related to the Public Holidays calendar which is still active and needed. I'm looking forward to the next version which hopefully resolves this issue completely.

This review is for a previous version of the add-on (1.0.4). 

Yes, there is. This may be the issue with the Birthdays Calendar. Please unsubscribe from this calendar until I release the next version. Aside from that, the first sync always takes a while, it should be fast after that.