It always took me nearly half a day to completely drain the iPhone battery with the iPod functionality, but now I have the possibility to do it in less then 2 hours :P
Oh and to increase the provider costs a little, do this:
Settings => General => Networks => EDGE
APN => Internet
Username => leave empty
Password => leave empty
And you should see the 'E' light up when you are lucky enough to be WiFi-less and all should work as slow & expensive as one can expect from a GPRS connection.
To get MMS to work on KPN, do: