Which is the same problem I have with my current WinMO phone, I can tether my laptop, but not my iPad.
If you have a WinMO phone, go to ppcgeeks, hack it and install WiFi router.
It's what I use on my touch pro 2 and it's amazing. Impossible to detect a tether and no additional costs from providers. Stealth tether FTW!
ON a different related note, I have had so many issues with a wireless connection in my living room, but the iPad has been pretty darn solid. Once every few days I might have an issue, but that's even debatable.
Download speeds are great, and the whole thing is pretty fantastic.