I'm in a 2007 only client environment, so i dont'; have any experience with other Outlook versions
Others may be able to comment on the difference and perhaps some more technical as opposed to behavioral things on calendar issues....If I can state my opinion, though, my experience has been that many if not most of the calendar sync issues can be corrected with user "behavior modification", and the items mentioned above. I've always found it to be best to be totally candid with executives on sync issues. My opinion is that a really big piece of the problem you described when you said,"one big VP has multiple delegates that much around'. A while back we looked in what Microsoft called their best practices for Outlook and even they suggested that the number of delegates be minimized...ideally one principle and one delegate..I undertand this sometimes isn't possible, but it is really best. When our users report an issue like this, we try and get principle and delegate to agree on a common strategy for appointment acceptance and scheduling. Good luck, I know this issue can be a real bugaboo