Hello.
We were looking in to this and had decided to use ADO 1.21 with Exchange 5.5.
However, before implementing it we moved to Exchange 6.0, started using XML, and we're very happy. One of my coworkers has come up with an on demand replacement for GetFreeBusy that only takes a couple of seconds for twelve busy calendars using C#(just to give you an idea of what is possible).
Everett Wilson
ewilson10@yahoo.com