We use it or something very similar and our bills are very low done nothing scientific but basically see the 1.50 charges on bill (bT) and no other charges.
The service seems to be ok for a LD cheapo line i think the missus as only been cut off a few times or had resaon to redial which is pretty good going considing the amount she uses the phone to phill. This is important as you know as the 5p connection fee uses up your credit amount if your not careful.
