Hi Chris... that is a slightly different service. It is more similar to the more familiar TopUp services run by Finarea here in the UK, where you top up by SMS... but then call a geographic number and use it as a gateway to international calls.
The unique thing with this service on the other hand is that you do not call the geographic service, you just ring it, and then you get a call back to your mobile.

The rates are gradually creeping upwards. UK landlines went up to 2p about a week ago, and today Australia, Georgia, Italy, Spain and USA went from 0,1,1,0,0 to 5p each, so no more unlimited calls for just the 5p connect fee.

5 p rates to landlines could almost be supportable longer-term, but I reckon they'll end up about 6 to 9p. Many mobiles are 25p, though Belgium France Germany and a couple of other Europeans are still 9 or 10p.

It can be used via a callthrough as well, such as 18185 or Voipbuster (yes, the call will go through the same server twice, and RC does send the caller ID of the calledback phone), though whether this is worthwhile depends on call rates