Google Contacts vs. Outlook
With Google Apps Sync for Microsoft Outlook®, you can access your same contacts from the Google Apps interface that you see in Microsoft® Outlook. These include your personal contacts as well as any global contacts set up for your domain.
When coming from Outlook, here are a few things to note.
In Google Apps contacts you can...
View the same personal contacts available in Outlook: Google Apps Sync imports and synchronizes nearly all of your personal contact information between Outlook and the Google Apps interface. Look up any contact under "My Contacts" or when entering addresses in mail messages.
View your global contacts, too, including all data fields your administrator has made available in your domain's Global Address List.
Add contact information Outlook doesn't support, such as "Google Voice." In Outlook, this information appears as a read-only attachment to the contact.
You might also want to...
Recreate your personal distribution lists as Google groups: Google Apps Sync doesn't synchronize your personal distribution lists between Outlook and your contacts in Google Apps. This means that lists you create in Outlook aren't automatically available from Google Apps. To send mail from Google Apps to the same lists you send to from Outlook, recreate your lists in Google Apps as personal Google groups.
Recreate your contact folders as groups, too: In Outlook, you can organize contacts in separate folders, such as one for work and one for family and friends. When synchronized with Google Apps, however, contacts from all your personal folders appear together in Google contacts, under "My Contacts." To match the same organization in Google Apps that you use in Outlook, use Google's personal groups feature, as well.
However you should avoid...
Updating contacts from Google Apps (if you're still using Outlook, too): Currently, updating a contact from the Google Apps interface can cause unexpected results in Outlook. For example, a full name in Google Apps might appear as a first name or last name in Outlook. Or you might receive a conflict error. Also, if you update a Notes field in Google Apps, your updates don't appear in Outlook, and subsequent updates in Outlook overwrite changes made in Google Apps.
This restriction doesn't apply if you're switching permanently to using Google Apps, in which case you can go ahead and update your Google contacts as much as you want.
And the following aren't available...
Contact follow-up flags: You can flag a contact for follow-up in Outlook so it appears on your To-Do list. However, contact flags don't get synchronized with the cloud and therefore aren't available in the Google Apps interface.
Categories: Google Apps contacts don't have a feature equivalent to Outlook categories, so any categories you assign to a contact in Outlook don't appear in Google Apps.
Rich formatting in descriptions: Links, bolding, and other rich content added in Outlook to a contact's Notes field, appear as plain text in Google Apps.
Contact notes larger than 16 kilobytes: Notes larger than 16 kb entered in an Outlook contact are currently truncated in the Google Apps interface. The full note, however, remains available in Outlook.