Q: how to maintain iTunes playlists

It's simple: copy the "iTunes Library.itl" that you have in your PC and move it to your Mac. This file is in the "iTunes" folder, and you must copy it in the "iTunes" folder of your Mac with iTunes closed. Finally, just open iTunes in your Mac.

Didi you read and follow the instructions in the link you came from?

-> Switch 101: Migrate your Windows files or system to your Mac

Don't move just the media.

Copy the entire /Music/iTunes/ folder from old computer to /Music/ on new computer.

Also, see this -> OS X Lion: About Windows Migration Assistant to migrate all your data.