My two (very large) cents:
Jailbreaking and unlocking of the iPad would be a good thing, in my opinion. I would happily go with a 3G model, but where on any given year I can be spending equal amounts of time in the US and Canada, being able to swap out SIM Cards like I do with my jailbroken iPhone would ideally make me happy as a clam.
With regards to tethering and iPhone/iPad Carriers: As you may have figured out from reading the last paragraph, I have two different cell phone plans in two different countries. You would be amazed that the different mentalities between the two when it comes to offering customers wireless service. AT&T, hailing from the land of the free, advertises "unlimited" data for $30. Bell Mobility, which hails from the land where wireless usage is governed by the CRTC, charges me $40 for a measly 500 MB. You'd be amazed at how that one little word - "unlimited" - governs your usage... in the US I really don't think twice about usage, whereas in Canada, I do. It's a bit of a placebo effect - even though I had reviewed my old AT&T bills before signing up with a Bell data plan and I had never ever gone over, say, 300 MB of data use per month, somehow overages with Bell are still in the back of my mind. It's silly, I know, it's not like there's a Canadian MB and a US MB, but still, it illustrates my point.
What is counterintuitive to this logic is that AT&T is having a shitfit about tethering because it foolishly tossed around that u-word when describing their data plan. Big bad AT&T is smart enough to know that if they were to allow tethering, Americans will test the limits the "unlimited" capabilities, as we sometimes see in these news articles that come up about Joe Blow who got a bill for $20 000 in data usage for something that was supposedly legitimate use. Amazingly enough, the Canadian carriers allow tethering - but the caveat is that it will eat into your 500 MB, so the notion is that, yes, you can tether, but it will be at a cost to yourself in the long run, so you'd better not tether very much or you won't have enough MB's left for your regular iPhone usage.
So, while a 3G model would be nice, regardless of location any heavy internet user would be looking for a way around these constraints, likely through jailbreaking, which brings me back to my original point, jailbreaking an iPad would be a very very good thing, not only for internet but for greater access to ebooks, apps, etc. as well.