[Przemolog]

Originally Posted by dem

Thanks very much for all of the replies. To answer some questions, my boyfriend travles to a different location in a different part of the world each time he takes a trip. There is no rhyme or reason to his plans. His last trip was to Austria, before that, the Amazon, before that, China.

So far so good. If by "Amazon" you mean Brazil, United Mobile would be OK. In the above mentioned countries incoming calls are free, and calls to the USA (or to the voicemail) cost 39 eurocents per minut + 25 eurocents
first minute surcharge. The same rate are valid in most Europe and some non-European countries.
The account may be autorecharged if the balance drops 10 euro.

Originally Posted by dem

His next trip will be to New Zealand. So I basically need something with wide coverage.

Here come troubles - UM has no coverage in New Zealand.

Originally Posted by dem

Re payment, I would prefer a company that deals in dollars, just to keep things easy. I like an auto recharge feature, but having a manual recharge feature is ok too. (In fact, he may prefer that.)

United Mobile, 09 and Travelsim charge in euros.
Hop, Yackie and multiple SIMs with Isle of Man numbers charge in dollars (although there are Man SIMs charged in euros.

As to phone issues, I meant some technical requirements. All so-called international SIMs use callback technology when making calls. This means that you dial the number, the connection is broken and the service provider call you back and the "proper" connection is being established.
The crucial point in comfortable using this technologuy is that not all phones can handle callback in this way. Some of them require using fancy menus or completing the destination number with some extra codes.
Moreover, if the phone is to be used worldwide, it must support four GSM frequency bands 850/900/1800/1900 MHz (so called "quadband"). If Korea and Japan are possible your boyfriends's travel destination, please notice that there's no GSM networks there and the phone would have also support WCDDA 2100 (aka 3G/UMTS).

Originally Posted by dem

The things that interest me the most are the reliability and helpfulness of the company, coverage of the SIM, and ease of use. These things are more important than price.

You must realise that there's no SIM which works everywhere where GSM networks are . If you care about coverage then your choice should be either 09 (Icelandic number, forgot Iceland when listing international SIM "home countries" ) or Yackie Mobile.
09 covers about 170 countries and it has free incoming calls in about 110 ones. However, rates from and to some countries are pretty high and there's no coverage in Switzerland - strange but true. Yackie also covers about 170 countries. It has paid incoming calls starting from $0.19/min but it has a US number which is forwarded to the mobile phone so you can call the number and national or even local rate (if numbers in your area are available). However, there have been many problems with Yackie. Since I don't have this SIM I can't tell you if it's realiable now - maybe those who have the one will tell...