Using Google Apps Sync is a great solution for this issue, but at the same time there can be issues that pop up when trying to sync up with Google's mail servers. For this reason, one of the best ways to troubleshoot issues is by obtaining the trace files, which are essentially Google Apps Sync's log files. These can be analyzed by support specialists and Google consultants in order to diagnose problems.
Google Apps Sync trace files location:
Windows 7 / Windows Vista: C:\Users\your-user-name\AppData\Local\Google\Google Apps Sync\Tracing\
Windows XP: C:\Documents and Settings\your-user-name\Local Settings\Application Data\Google\Google Apps Sync\Tracing\
Unified Single Sign On trace files location:
Windows 7 / Windows Vista: C:\Users\your-user-name\AppData\Local\Google\Identity
Windows XP: C:\Documents and Settings\your-user-name\Local Settings\Application Data\Google\Identity
Another troubleshooting tip: checking out the Google Apps known issues resource. The Apps Sync issues will be seen under the "Email Clients and Mobile Devices" heading. This will tell you whether or not a problem you are experiencing may be something that others are also seeing, and that Google is aware of and attempting to work on a fix.
It's also helpful to understand the limitations of Google Apps Sync for Microsoft Outlook. For example, tasks are not capable of syncing with the client, calendar invites cannot be sent out to groups and the out of office messaging functionality is minimal at best.
With that being said, Google Apps Sync is still a nice stopgap, just as long as users understand it is not a permanent solution. That's really what Gmail is for when you go Google. Are you using Google Apps Sync for Microsoft Outlook? Have you found any problems or limitations with it?