I use Skype to call landline phones all over the world, but especially to the USA. I also paid for a US area code Skype telephone number with voice mail, and it is that number I give out to people who need to phone me from the States.
Most of the time the phone quality is good, but sometimes, though rarely, it is so bad that I need to hang up and call again. The price rate varies. I think it is 2 cents a minute to the States and some other western countries, but I also call places more far flung and difficult, and some of those calls run up to 7 cents a minute. But I compare that with more than a dollar a minute using an AT&T calling card for the same call.
I thought I would be charged (or see it deducted from the running total of credit in the Skype box) for even toll-free calls, like to 800 numbers. But I've noticed no deductions for 800 number calls, so apparently they are toll free on Skype.
Finally, I have in the past four years of using Skype this way, never had to contact customer service because I have never had a service problem. I don't have very high expectations for a service like Skype, so I am not disappointed. (Except the rare times I am paying 2 cents a minute for a call with bad sound quality.) I have not had a billing problem or seen any unauthorized charges. On the contrary, re. the free 800 calls, I think maybe they are not charging me for calls I expected to be charged for.
In short, works fine for my purposes.