I used to work at an ISP. In my humble opinion, it's SO expensive to use ipass for roaming, it's cheaper to sign up for a 3rd party carrier (like First Telecom) and make international calls rather than pay for ipass.
for example, I can ring the USA for less than 2.5 cents per minute from England.
there are other roaming providers of course other than ipass.
note that in the UK and much of europe, there are no-contract ISPs where your phone call (typically a low-rate call) pays for the cost of the access to the internet. Freeserve, now Wanadoo, offer this service ("pay as you go") as does Tiscali and others.
in practise, if you don't need access for too long, an open wifi point works ok :-)
