In reply to Andrew W:
I have a Nexus 7 with 3G, which does everything I want it to and worked happily with a Telenor SIM card.
Got the SIM card at the shop in Oslo Airport - 7 days of data for 200 NOK (I think - can't remember exactly but it seemed reasonable to me). Apparently the days aren't counted consecutively, you only use one up on a day when you actually access the internet.
The card could in theory be topped up online or by buying vouchers, but the Telenor website hated my credit card and I couldn't find anywhere to buy vouchers in Sjusjoen. I didn't look that hard as we were only there for eight days - and the card seemed to work right up till we left.
I've no experience with tablets or smartphones so it was a pleasant surprise that everything (except the credit card) worked so smoothly.