Sadly I have to agree... Rated 3 out of 5 stars
First, thank you to all who have worked on this project and all the hard work that has gone into it's progress. However, lack of calendaring has become an enterprise non starter and Lightning has been so close to making the grade, that to lose ground now is very disheartening. The fact that it has not been able to keep up with the releases of Thunderbird, makes it very difficult for those of us who want to advocate for it's use, to continue. Whatever improvements that are made are lost because the instability does not allow it to be used at all. For this small corporate user, it is a real loss.
When it works, it works well. There are some bugs with large or numerous calendars, but up until now, it has been very usable for our small creative workgroup. Please, don't make me use outlook.