Q: I just decommissioned my windows pc for a mac power book.  How can I get my ipad to sync with the new computer without erasing all the apps and data on the ipad?

If still have the PC, and did not wipe the hard drive, copy the iTunes libraries and backup files to flash drive then import them to the Mac.

Also, you can use Migration Assistant to just move all the files over to the Mac.

Migration Assistant for PC to Mac

Best option is to use Windows Migration Assistant as Ralph noted.

Here's a better (updated) link to Windows Migration Assistant for Lion -> http://support.apple.com/kb/HT4796

Or if you only want iTunes (Migration Assistant let's you choose) copy the entire /Music/iTunes/ folder from your PC to /Music/ on the Mac.

FYI: A MacBook is not a PowerBook. PowerBooks were discontinued in 2005.