Yes, I use VOIP all the time. I use Gigaset VOIP telephones using the Gigaset N300 AIP base station.
I then subscribe to
Easy option to save on your monthly calling charges right away., pays my €10 and get free landline calls for three months (have to pay for calls to mobile numbers). After that free period the cost of calls is taken from my €10 until I run low. I then buy another €10 worth and get another three months of free calls.
So cost of calls though my TalkTalk account is zero, and calls through voipdiscount amount to about €30 per year.
I am unable to detect any difference in call quality between VOIP and the regular service.
Oh, I nearly forgot I can use voipdiscount on my iPhone (because there is an app called Mobile VOIP) when I am using
any wifi network. The app links to my voipdiscount account.
Simples!