As I was cheapskate and did not buy 3G enabled iPad, Wifi tethering from my N900 has been a more and more important feature to me.
Initially I had tried MobileHotspot – which was available from regular Maemo repositories for free, but could not get it to work after firmware update was made to the phone. It is possible that in some time people will fix whatever is wrong with Mobile Hotspot – or then again it could have been something just on my phone. Nevertheless I decided not to spend any more time debugging and tinkering with it, and purchased for 9 euros Joikuspot – which promised to work on N900 with PR1.3 firmware.
And it worked.
There was just some problem with my iPad not getting ip via DHCP, while my Macbook worked just fine. Then again that did not hurt so much, as connection with iPad worked while setting own static ip, netmask and router information.
So unless Mobile hotspot works for you out of the box and/or you will find necessary information from the discussion above, then I suggest returning to vanilla kernel and use Joikuspot.