I love giffgaff, both my wife and I are on it:

£10 per month, 250 minutes, unlimited data*, unlimited texts* free giffgaff to giffgaff calls (up to 60 minutes per call).

Given that I call my wife the most (and vice versa), I actually hardly use any minutes per month.

Her iPad also uses the £10 gigabag, activated when needed. Would do the £5 one, but part of the giffgaff deal is that goodybags/gigabags run for a calendar month. If you happen to use all your allowance in the first day, then you drop onto the pay & go rates, you cannot buy another "bag" until the month is up.

I suppose we should really stockpile a bunch of sims and then swap if one gets overused.

Wish they did tethering though, it could be useful in the odd situation. Although saying that, the "low cost hotel chain" here in the UK has started allowing free 30 minutes of wifi per day......cough..mac address..cough.

I've always wondered (and googled, albeit not that in-depth) whether Mac OS is smart enough to know that your internet is being provided by a mobile network and therefore to not download software updates in the background (as mine is set to do) - I always thought that was a sure fire way to end up confused as to why all your data has gone.

(* unlimited means FUPPED)