According to what I have read, for example here http://sverigesradio.se/sida/artikel.aspx?programid=2151&artikel=4387324 the OP is not really correct.
1. Germany has had this system running since 2009.
2. Denmark will start using it from April 2011.
3. Sweden is just looking at having this kind of a solution.
And for all three, it is / will be only complimentary to regular stamps.
I just tried to print to my printer loaded with A4-papers. It worked! Finally. This has not worked until now (forced letter).
This is very common with software developed in the US, they seem to forget/not care/not being aware of that there are other countries in the world.I think most countries in the world use A4.