"You'll get me out of Outlook when you pry my cold, dead hands off the keyboard".... :-)
I'm sure you've got a few users who actually know how to use the product who feel the same way. Why not keep them happy, too? If your users enjoy the scheduling and other functionality of Outlook/Exchange (which goes well beyond the functionality of Google Apps at present, and not just for meeting scheduling), then it might be worthwhile to take a look at one of the open-source Exchange alternatives like Zimbra: www.zimbra.com Zimbra was bought by Yahoo recently, so it's at least potentially a target if MS buys Yahoo--not the best news, though it's open source, so the worst that MS could do is to shut off the direct Exchange integration, which wouldn't matter if you're leaving Exchange entirely. But Zimbra's a terrific collaborative environment, it's fully web-based, and it solves the lack-of-equivalent-functionality problem much more fully than do Gmail/GCal. You can install it yourself, or buy mailboxes from them in a hosting model. Zimbra's not the only such product, either, so if you like the idea you can find a few other OSS competitors using similar models that would also like to help you leave Exchange. Hope this helps, --Chris