Here are the main problem I see with rolling Google Apps out to Outlook users who are used to Exchange:

  1. Access to shared calendars won’t work the same
    1. I guess you could use something like OggSync to sync public and selected private calendars, but that is kludgey compared to Exchange free/busy functionality.
    2. Using the Google Apps web interface is probably almost as good, but there is usually a lot of resistance to this thin client approach.
    3. I played around with Outlook 2003 and iCal/WebDav for free-busy info, but it was a pain to set up.  I should revisit this and see if there is a better way to do it now.
  2. No Global Address Book
    1. I’m not sure how to address this.
  3. No Public Folders
    1. Does anyone really use these effectively anyway? Most of the uses I’ve seen could have been done a number of different ways.

Well one client recently didn’t see a problem with going down this route.  I would definitely put my money on Google over ZImbra, OpenGroupWare, etc..