@ChrisNeedsToKnow
According to
this post the Galaxy Nexus actually supports STK but - obviously due to a bug - the app will only appear if there is a PIN set for the SIM card.
During a trip via Luxembourg and Belgium to the Netherlands on the weekend I noticed that automatic IMSI switching works unreliably on my Nokia 1200. While crossing Luxembourg it didn't register on local networks, instead Belgian Base was the first roaming network my SIM did register to. But it did not switch to my Dutch IMSI for half an hour after I had entered the Netherlands. On my way home however it did automatically switch back from the Dutch to the Roaming IMSI after a couple of kilometres into Belgium.
Reliability of the automatic IMSI switchting probably very much depends on the STK implementation of the used handset. Unfortunately I don't see how IMSI switching could be improved since at least
Android doesn't provide an API for low level access to the SIM card so you cannot send the appropriate commands from an Android app to the SIM (
discussed here).