On my Nokia C2-00 automatic selection doesn´t seem to work at all.

On selecting anything in the STK (automatic, or one of the IMSIs), the phone crashes. After restarting, the selection I made comes into effect. However, when selecting "automatic" the phone doesn´t register in any network. Neither on manual nor automatic network selection.

As such I just select everything manually, and I don´t really mind about that. I guess that´s because of the phone.

Which country are you in?

From what I've read here (and my own experience), in the Toggle countries it will only register on the localized IMSI for the country you are in. If you are not in one of the Toggle countries, it will only register on the roaming IMSI.

@ChrisNeedsToKnow
STK implementation has ever been quite buggy, especially when the STK application does odd things like resetting the SIM (which toggle does when the IMSI is being changed). Back in the days of United Mobile some phones even crashed when placing an outgoing call (which should have made the STK requesting a callback by USSD) while others simply aborted the call. Perhaps a firmware update can solve your issue.

Toggle (and Other Multiple IMSI Cards) Don't Play Well With Google/Gmail Products
 

Google has an annoying security feature on Android phones- every time you change the SIM card, you have to log into Google again. So, no Gmail, no Play Store, etc. until you log back in.

Of course, Google sees and IMSI change as a change of SIM card.

This is a particular pain for people like myself who use two-step authentication. You have to use a non-memorable Google generated "application specific password."

There is likewise an annoying process on iPhones when you switch SIM cards. The iPhone sends a chargeable SMS to +44 7786 205094 and/or +44 7537 4102X1. These numbers are Apple's iMessage and FaceTime activation servers hosted by Vodafone UK. Presumably this happens on the iPhone every time you change IMSI; it certainly happens with an Orange UK SIM card when switching between lines on Enhanced Line 2. As Toggle have yet to issue nano-SIMs, I haven't been able to test this yet on my iPhone 5.

I wonder where the "order" to send the SMS originates? I would have a hard time believing that the phone issues the order, given that Iphones are sold around the world and I doubt that an Iphone in the US for example would send an SMS to the UK. Was the Iphone in question originally locked to Vodafone?

BTW, I have a Toggle nano SIM - it was a regular one that I cut down to size using a SIM cutter and it works fine.

The iPhone gives the order to send the SMS. It displays a warning the first time a SIM is inserted but doesn't do so on subsequent insertions of the same SIM. It is puzzling that the iPhone can remember a previously used SIM card with regard to the warning message but still needs to send the text to verify the SIM's phone number when it has already done so for the same SIM in the past.

All iPhones send SMS to these Vodafone UK numbers, irrespective of who supplied the iPhone or SIM card. If you look around various forums, you will see complaints about this from many countries. There are rarely complaints from UK users because most UK users have inclusive SMS to other UK mobile numbers; the problem affects UK users only when roaming. Many (but not all) iPhone supported carriers suppress the charges for SMS to these numbers. I also believe that a US number has been introduced to run in parallel with the Vodafone UK numbers, although the iPhone's criteria for its selection are not clear.

I'm wondering when will Lycamobile use the assigned italian MNC to issue sim-cards (along with its new assigned italian mobile prefix: 351 0)

I think that when they're ready, they will use them to provide also IMSI and local numbers to Toggle customers.

Thanks for the hint. The C2-00´s firmware is up-to-date. Luckily I only use it as a backup phone. I´d love to see an official "direct"-Google-Android-dual-SIM mobile, but I guess that will have to wait.

Over the weekend in Spain toogle worked like a charm. Incoming calls on my Swiss number reached me free of charge. It´s as if the EU´s plan to abolish roamingcharges was already true now, incl Switzerland :)

Last but not least I found out that my Samsung i9250 ("Galaxy Nexus") does not support STK, there´s simply no menu. However, changes made on the C2-00 seem to be saved on the SIM, so it´s just a matter of changing settings first, and swapping the SIM after. For me, not crossing the border every day, this is not great but acceptable.

I´m now looking for a solution to automate the toggle D/CH network switch for a friend from Konstanz/Germany, who crosses the border all the time. Switching manually every day would be a pain. He lives so close to the border that all networks (4German 3Swiss) are available. I hope this won´t dry the battery on automatic mode. Will report back with findings once I have them, but this will take a while...

@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).