I received my N73 last week, as an upgrade on O2.
My current SIM card is out of my Sony Ericsson K750i, which is 2G. However, I received a 3G SIM card with my new Nokia.
At the moment I'm using my old 2G SIM, which is all working fine. Has anyone else had an upgrade on O2 for a N73 and used the 3G SIM card? Did you benefit much from it?