P2T, PTT, Push-to-talk

Hi there, Push-to-Talk users,

Since P2T is not very well known yet in Europe (still in it's preliminary
phase), maybe some of you could help me out with some of the questions I
have concerning this subject :
-What are the main advantages of P2T compared to SMS, e.g. or, the other way
around, the main disadvantages ?
-Does anyone know about any P2T pilot-projects in Europe that might be
interesting to know about?
-Does any of you have any experience in a professional environment
(dispatching, service departments, logistics...) , and if so, can anyone
tell me why I should consider introducing this rather new medium in my
company?
-Does anyone know any figures about the cost/head related to P2T, when used
in a professional environment?
-Who are the main players, next to Nextel and eStara in the world, and maybe
more in particular, in Europe?

If you have any interesting facts related to any of my questions (and in
particular the American and Australian users), please post your reply's
here, or send an e-mail.

Best regards,

Danny