Aricarai - I was nervous about that at first as well. You never give them your credit card information, but that first month afterwards when I opened up my cell phone bill I was holding my breath, waiting for the kick in the gut.
Never happened. I've been using it for a couple months now and my cell phone bill has never increased even one penny. Basically you are both using local numbers. As long as the number they give him on his side (the one which shows up on his phone when you call him) is local you'll be fine. It's literally the same as calling someone who's across the street.
I have noticed that occassionally the line doesn't work. There will be nothing but silence when you dial and you can't connect to your person. But usually you just try again in ten minutes and everything's fine. Hey, it's free, so I don't expect the perfection I would if it were a paid service.
Oh, and my fiance never had to sign up for the service or even visit the website. All he has to do is just use the London number to call me. Your boyfriend doesn't have to join anything.
I live on Lahaina side of Maui. It's gorgeous here and I'm trying to soak up as much sun and warmth as possible before I make the big move to England after my April wedding.
Which island is your parent's place on?