Every now and then I am in a country where network operators are making it difficult for me with their limited network coverage to make phone calls and surf the web in places like hotel lobbies, restaurants, meeting rooms, hotel rooms, you name it. In one place one network operator has some sort of coverage while in another place, if you are lucky, only a competitor can be received. So I could in theory just switch my phone to automatic network selection but that would mean that the Internet connection of my phone is reestablished every 5 minutes, which is not acceptable from convenience and monetary point of view.
So one of these days when I was stuck without network coverage again and contemplating to switch to another network for some time, I wondered if a Dual-SIM phone would also do the trick for me. One SIM card locked to one network, one SIM Card locked to another and call forwarding when not reachable on both sides to the other. And for outgoing calls I use the SIM card and network that is available at the time. Ugly, but reachability and instant usability would skyrocket :-)