Im a big truphone evangelist..they've set the path for mobile VoIP..and even though I wasnt using it that much before I am now..
- calls are FREE for the rest of the year (not only to other truphone users) but also to landlines (and some mobile numbers) at no cost in all 40 countries until the end of 2007!! here is the list of those countries
-more cool features like VoIP over 3G, presence and free SMS messages..the much improved wi-fi access feature is awesome..no more SIP profiles..I can now search for an access point and start using truphone in less than a minute read more here
-they also support gtalk as well and I hope soon they will also support the N800 internet tablet to compete right up against skype and gizmo (compete? i think not..more like own it)