I have 900+ contacts I had to transfer and backup, and I was able to do it without problems. Reminder: Google has "Remove/Merge Duplicates" feature.
Directions for both Cupcake (1.5) and Eclair (2.1).
- Turn off Google Sync for Contacts for the time being (If you have it on).
- Go to People > Click Menu > Import/Export > Export to SD Card.
(IF YOU ARE RUNNING 1.5:, Download "exportcontacts" by rishi srivatsaval from the Market and use that program to export contacts to your SD card)
- Mount your Eris to your computer and copy the exported contacts file to your computer.
- Go to Google Contacts (http://google.com/contacts) > Contacts > Export and export all your Google contacts. (As backup)
- Delete all your contacts on your phone.
- Go back to Google Contacts and import your phone contacts.
- After you import them, you should see on the right iFrame a "Find duplicates" feature. Run it, do what you need to do to remove or merge duplicates.
- Turn your Google Sync for Contacts back on your phone and sync!
If you got any other questions, I'd be more than happy to help.