I haven't done this but perhaps you can locate and copy the iPad backup to an external drive.
User... /Library/Application Support/MobileSync/Backup
Or
C:\Documents and Settings\YOUR_USER_NAME\Application Data\Apple Computer\SyncServices\Local
Then load it to the new computer and "restore from backup" on iTunes once you connect the iPad.
Now, again, I don't know if this will work as I have not tried it. It however would be a great thing to do with my iPod Touch. I have that currently on my iMac and would prefer it on the Mac Pro. I might try this tomorrow. Theoretically, if it doesn't work, I can always restore it back from the iMac backup.
EDIT: Read this thread in the iPhone forums. It should work the same way.