Early last year I invested in a SNOM 300 VoIP phone for /dev/girlfriends's house in Somerset West.. so I could make the odd 10min+ phone call (from Gardens or Newlands) without paying my most loved GSM providers and without frying my scone... erm, brain.
Looking at my E61's call log tonight, I've used 905 VoIP minutes... ~15 hours.
My GSM contract per minute rate is between R1 and R2 (off/on peak). So even at off-peak rates I've recovered the cost of the SNOM 300 phone (-:
The other interesting thing to note is that my VoIP calls are 100% free. No such thing as a free lunch? In this case it's really free (for me).. Calls route over the Amobia network end to end... (60km+)
More interesting is that I think the voice quality is usually better than a GSM call.
In April last year the Frogfoot office switched to using SIP/VoIP. Some pics.
Since then 4 people also use the SIP clients on their mobile phones to connect to the PBX. Nokia E61, E61i, N95 and E65 all work well.
I'm impressed by the adoption rates for VoIP/SIP, Asterisk and nomadic telephony (VoWifi).
We now have an SRV DNS record to start moving towards a UID-style dialing system.. (email@example.com).. but we're still playing with this... it's firewalled for now.
root@blue[~]# dig _sip._udp.frogfoot.com srv
;; QUESTION SECTION:
;_sip._udp.frogfoot.com. IN SRV
;; ANSWER SECTION:
_sip._udp.frogfoot.com. 86400 IN SRV 5 0 5060 pbx.frogfoot.com.