So, after a little while waiting, we now have an iPad wifi+3G 64gb version for our main portable. While all our development work has to stay on the Mac, our Macbook Air will go our to pasture.
At this stage we are using the iPad on wifi 99% of the time, but it has a prepay SIM loaded for that occasional use. There is a school of thought which says to hack your iPhone and use a tether system, no point, and who wants a hacked phone when a simple prepay data SIM is so easy to get!
So far, it is just an iPad, walk out onto the street, and it still an iPad! The wifi version without a data connection is kinda like a dataless piece of glass.