ScheduleOnce is not just the best way to find common slots of free time for a group of busy people, it is the only practical way!
Using ScheduleOnce has spared me and my colleagues endless streams of phone calls for each online video meeting, calls which are both expensive and frustrating. Organizing conferences through phone calls is a sequential process, which means that more often than not the first calls have to be repeated to allow for new circumstances arising from successive calls.
ScheduleOnce, as the second part of the name implies, frees you from these second - and more - rounds of calls, or from a cumbersome series of e-mails.
I strongly recommend ScheduleOnce as the only practical way to organize meetings.