Yup, I'm in the same boat as you. My HP wireless printer uses a generic driver, but hey it works. Something I couldn't do with my iPadv1.
What HP printer model do you have? I'm want to buy and use a black and white wireless laser printer on my RT and I am having a hard time finding a compatible device. The compatibility center is really only useful for checking a given model not finding one with certain characteristics.
My RT is only a few days old ... you say that you used a generic driver ... is there documentation on how to do this on an RT running 8.1?