For anyone dreading doing it, don't be. It's actually a fairly easy process and I got there around 11am and done by 12.30. In the Kai Tak centre you just queue to get told which letter office you need to go to, take the lift up to the designated office, fill in your tax form (remember to at least keep softcopy proof) of your TVCs etc for the previous and current tax years (previous one if you have yet to be billed, which was true of my case). You'll wait a bit for the tax officer to do the computation and call your name when he or she is done. They will run through it and get you to sign an acknowledgement. I got a refund so I got my release letter immediately and job done! They will only post you a refund via cheque so you need an address to receive it (perhaps a friend or relative can let you use their address).
Good luck!
HK efficiency wins again!