I'm planning to buy an ipad 2 and was told to buy the at&t model as it's easier to activatite in countries outside the US with GSM cellular system. Can someone advise if this is right and what needs to be done to make sure it will work with a non US GSM sim card

Only the AT&T iPad will work outside the USA. The Verizon model will only work in the US and a very few other countries. Many members have successfully purchased iPads in the USA and have had no trouble getting them to work with non-AT&T SIM cards, although there has been a discussion as to whether the iPad needs to have its 3G activated initially in the US. Most Members choose this safe route and activate their iPads in the US. We have a mix of other Members who have not - some have reported difficulties in activating their iPads when they got home (having not done so in the US) while others seem to have no problems at all.

Tim

Good to know, Tim! Of course you would know it.

True and AT&T version is continuously imported to HK's gray market from the beginning till now and they sell to other countries as well.

Just to clarify the info from Tim's post: I bought an iPad in the US. I activated an AT&T 3G account. I am moving to England where my husband uses Vodafone for mobile service. Vodafone offers 3G for iPads. Should I expect a Vodafone chip to work with my 3G after I remove the AT&T chip so I do not have to pay roaming fees back to the US?