>Some of us want to retain a fixed schedule, as a means of allowing the members and guests to pre-schedule known dates for attending events expected to be of interest. Others feel its easier to schedule events around the speakers, and just 'spam' the mailing list to let people know the latest schedule as it gets set up.

I feel that a fixed schedule is better. In the Vancouver group, if someone special comes to town and we have a meeting when it suits their schedule. If it falls really close to the normal meeting time (same week) we cancel the regular meeting. Regular meetings (I believe) attract new users and give momentum to the group.