Ive been using them for maybe 6-12 months. Maybe the old glitch, but pretty good otherwise. They were one of the first to allow you to send your landline CND on a voip call which a gripe from my better half.
One thing I would suggest is look at your calling patterns. While 8c a call looks cheap I still analyse my calling patterns and am still better off on their timed plan (1.6c /min).
I'm pretty sure an average phone call is only about 3 mins, think of all the times you call and get voicemail or answering machines all call for quick enquiries.
You'd have to average 5 mins per call before you're better off with 8c untimed.
Best of luck!