What's more painful and time consuming than entering in 300 of your contacts into a new cellphone? Entering 400 contacts into a new cellphone. Screw that. With the Zyb online service, you can back up your contacts ala the T-Mobile Sidekick, so you'll never have to do that again.
The Zyb service supports 200 types of phones, and once backed up, your contacts can be managed using a web interface and shared with other Zyb users. The service is based on the SyncML data interface, so most phones should be able to use it. Check the list to see if yours is supported. Best yet, the service is free.