I use VoIP, but rarely Skype. SkHype I find is often a bit unreliable, maybe as I don't have QoS set for it on router.
Big prob for me is the bloody computer needs to be on.
Hence I use a SIP adapter, and have a real phone plugged in, so no computers need to be on. I then obviously use a standard SIP provider (SkHype is non standard).
My provider isn't the cheapest, but does have free signup/rental/geographic number (so landlines calling you don't pay a fortune). I use it mainly to chat to family on VoIP, or overseas relatives on their landlines. And Mrs TB's mobile.
The one person its not great to is my Mum on Plusnet, but thats because Plusnet are scumbags, giving higher priority to their VoIP service, and lower to anyone elses.
For other geographic UK numbers, I have free evening/weekends calls from BT (offered free if you commit to another 12 months), and an outstanding call package on her mobile to call other mobiles)
My BT calls bill is usually less than £2 per quarter.
In affect, I have 4 lines coming in - my own home one, with Zen broadband on it, a works provided line with some flavour of BT Broadband on it (all fully paid, calls as well), a geographic VoIP, and a 0845 VoIP, all wired into a Norstar so I can deal with any line from any room in house.