I have just started working with ACE Meetings, but so far, I like it.
It's not a perfect tool yet, but Customer Support is excellent. And that's what I expect from an AppSumo offer.
One thing I liked a lot was that I could customize the messages for each type of event. However, it would be essential to be able to send at least 2 reminders per scheduled meeting. I usually send 24h and 1h reminders.
I'm giving 5 tacos since I feel like they're eager to improve the tool and make it state-of-the-art, and it's a great value-for-money deal!