international travellers - best kind of cellphone to have?

So far I’ve managed by buying a cheap pay-as-you-go cellphone wherever I happen to be, but I’m wondering if there’s a better option. Most of my travel is to the US and the UK. I’m thinking either -

Buy a cellphone that allows me to switch out the sim card freely.

Buy a cellphone that allows roaming. (I don’t use my phone often when I’m abroad, just when I need to contact someone - extended conversations take place on Skype)

Buy an iPhone and use Skype when I’m abroad.

Any advice? I have to admit - I really want to buy an iPhone but I’m not sure about the practicality of using it abroad. Has anyone used Skype on the iPhone? Does it work well?

In my opinion, the best option is to buy a phone that allows you to swap out the SIM card. My phone allows roaming, but if I leave my Qatari SIM card in and travel to (say) Lebanon, if a friend wants to meet for lunch, they have to make an international call to reach me, even if I’m three blocks away! So I just buy a local SIM card for the duration of my stay, and then replace my Qatari SIM card when I go home. If you are only making outgoing calls, it’s maybe not so much of a problem, but if you want people to be able to reach you, then it really is convenient to have a local phone # for your stay.

This might be more difficult in the States. I went to the US in December and went to a T-Mobile store to try to buy a SIM card, but was told they didn’t use SIM cards; I had to buy a throw away phone (which was so cheap that it really didn’t matter). But maybe other providers use SIM cards in the US? I don’t know; some knowledgeable US dopers can check in on that.

You’re in Korea most of the time, which uses some proprietary systems. GPRS phones are more widely available than other formats. Check out the country formats for where you travel.

Otherwise, an unlocked phone is the answer. But do check if it’s GPRS or CDMA or something else.

I guess this is a dumb question, but you can’t swap out the sim card on an iPhone?

I have a knackered old unlocked Nokia for this purpose. I buy a local SIM wherever I go. However, if you include the US in the equation, you need an unlocked triband phone.

Maybe think too about getting one of those international roaming SIMs that has a low-cost dial-in number in each country. I can’t remember the name of the company and I can’t find it via Google, but they sell them in the in-flight shopping service on Virgin Atlantic, and probably some other airlines too.

Skype on my iPhone works fine. But because I jailbroke and unlocked my iPhone, I just use a local SIM card for voice calls and data (mostly, data, which could be Skype in your case). If you want to use Skype over 3G, though, you’ll have to jailbreak it an install “3G Unrestrictor.”