I mentioned HiPerExchange a couple of days ago but it was only this morning, as I logged onto Outlook, that I realized Microsoft have rather spoiled the point of this product with Outlook 2003. This version of Outlook has Cached Exchange Mode which seems to serve the same purpose as HiPerExchange:
Outlook 2003 clients using Cached Exchange Mode perform most e-mail-related tasks from the local client, reducing the number of requests to the server for data and improving performance for items stored in the local copy of the mailbox or .ost file. After the full copy of a user mailbox and offline address book is downloaded, Cached Exchange Mode significantly reduces network bandwidth consumption for e-mail between the client and server. This greatly improves the Outlook experience for remote or branch office users as well as removes the need to restart Outlook to an offline profile when network interruptions occur.
The 800-lb gorilla strikes again. But, seriously, it was an obvious enhancement for Microsoft to make so the Seaside people can't really complain. Oh well, as I said, HiPerExchange must have been a cool project to work on.
I'm using Outlook 2003 in this mode and it does seem to handle online/offline much better than previous versions. More details of Outlook 2003 improvements, performance and otherwise, here.