I'm interested on how the move towards use of end-user SIP phones will affect the roaming SIM market. Many of us have seperate SIM and SIP (or Skype) services which are not well joined-up. One number (or set of numbers) which rings on whatever devices is handy - and allow any device to be used for outgoing - it seems like a good idea to me, but is it too complex for normal users (i.e. non-PrepaidGSM-readers!) to fathom.
And, in anticipation of the next few messages, I know there are many providers with this functionality 'just around the corner'
Micky