Does anyone recomend the Telestial Passport?

Generally, everything that Telestial sells has a big markup. I wouldn't expect anything less for this offering.

Generally these "works everywhere" GSM SIM cards have rates less egregious than using roaming minutes with your home service they're a good deal more expensive than the rates you'd get on a country specific card. Country specific cards are easily available in most countries and provide much better value. Many come with starter accounts that come with some credit (typically €10 or so in Europe) and the card itself often is around €10 for a starter account.

 

I don't think its worth it. Just get a local sim card for outgoing calls.

 

I would recommend checking the http://www.prepaidgsm.net/forum/international-gsm-prepaid-cards/ for a lot of info dedicated to these global roaming SIMs, as well as better deals than Telestial. Sorry, don't know about South Korea.

 

I could't tell you if they have the best rates or not but I have used them in the past therefore I can share my experience with you .

My reason for purchasing their SIM was based on the fact that we were going to be in 3 different countries in 3 weeks and I did not want to deal with purchasing 3 different local SIM's and call back home and give those numbers to everyone.
As far as making calls, it is not a direct dial service. So you dial the number you want and hang up the phone.; few seconds later (sometimes up to a minute) your phone rings and when you answer your phone you get connected to the number you were trying to reach. This part worked well. We called home almost everyday and connection was clear.
The part that did not work well was when anyone tried called us. It was a hit and miss. Sometimes they would get a hold of us other times our phone would not ring at all.
So in conclusion, after using them couple of times, I decided to activate the international plan on my att line and pay the difference in price (if I am not mistaking it was around 40 cents/minute) so i would not have to worry about missing any important calls.

Also just as an FYI, last year's vacation I told everyone at home to call us only if there was an emergency and we would check in with them via Skype on a regular basis. It worked great as we found open internet connections just about anywhere we went.