Word of caution: Any address or email address you provide will likely be bombarded with junk!
I subscribed to some magazines a while back with a special deal (not quite free) and it was a great deal, but I used a temporary email address, and I used the first name "BobMag" so I could id mail sent because of it. I still get lots of mail to BobMag! But it's nice to know where it came from!
Still sounds like a great deal though. And IBM/PC World might not be as brazen with your info. In fact, I might try this deal myself using the same method. Except I'd actually be interested in the newsletter also, so might use a more legitimate email address with it.