A small one
Excellent call clarity and cheapness of calls allows me to call my girlfriend in Sydney for absolutely nothing. For £7.99 the Vonage line has given us both a lifeline away from other more expensive and less reliable VOIP services and calling cards. Customer services, in my own experience have always been second to none. I am unsure of the other posters comments and experiences but I have been a user in the UK for over a year now and have been fully satisfied with the service. Customer services even credited me back an extra bonus on my bill for overcharging me one month. This was offered without having to ask or complain at all. Tech support is always helpful and knowledgeable and are always at hand to help. You can also take the box with you anywhere and connect it to any broadband connection, although some countries in the Middle East and in Sub-continent block the ip addresses used by Vonage for some reason. I may also have to move over to Skype in order to make "free" calls as required and I am slightly P@ssed about this due to the same service being slightly more expensive.
No complaints about Vonage apart from very rarely (appx once a month) I might have to reset the connection by re-booting the system and reconnecting the wires. This is a relatively simple task that takes a few minutes. Call quality is dependent upon the speed of you Broadband connection you have and if you are also downloading at the same time and using up bandwidth. I have recently moved over to O2 broadband with a juicy 16MB connection that seems to be the perfect set up. I have not had a problem since moving from a slower Aol connection to O2.
My only real complaint is that free services are not (as yet) available to landlines in the Indian Sub-Continent, namely Sri Lanka but I am sure that this will be sorted out with time. Once you get used to the set up and the very occasional rebooting that is required (I haven't done this in over a month now) then it is all smooth sailing.
Loads of features such as caller display and call forwarding / call blocking etc. They don't cap and ask you to redial after an hour on the same call. Can see what calls have been made on the internet immediately and changes can be made. View your account online. Many many good features.
Only very occasionally you may get a message saying that lines are busy and try later which can be annoying.
I have been using Vonage for over 12 months now and never experienced any serious issues, call quality is excellent, I phone the States, Australia, Spain, Ireland and obviously the UK and always have clear and precise conversations. I can keep a tab on my bill within seconds of a call ending although the package of £7.99 per month is rarely exceeded. They keep adding new countries that you can dial every so often and you will have to phone them and ask to be transferred to the latest plan, they always do this free of charge. My overall impression is that Vonage offer excellent value as I'm sure other voip companies probably do. I will not change unless a competitor offers something much more substantial. Very happy user.
Loads of free, very useful functionality, with probably the lowest line rental around.
Excellent customer service.
Operation depends entirely on availability of Ethernet broadband Internet connection and mains electricity; so may not be used as an emergency phone. And, initial set up fee of about £17 (as of 3rd November 2006).
Vonage is excellent as a land phone if you have mobile phones already.
UK land phone for £7.99 per month. You get unlimited free calls, all day, to landlines in UK, Ireland, US, Canada, France, Italy and Spain.
Free phone adapter (worth £30), Voicemail, Caller Display, Call Waiting, Call Diversion, 3-Way Calling, Call Transfer, 1471, Withhold Caller Display, Ring Back, International Call Barring, etc.
Vonage has excellent customer service, which is almost unheard of in the UK. Highly recommended.