Should I disconnect appliances if there is lightning?
Generally, a device that is not plugged into the wall will have a greater chance of surviving a mains-borne impulse than one that is. A device that is connected several times, so an antenna amplifier connected to both supply and antennae, an ADSL router connected to supply, the phone line and computers, will be much more vulnerable than something that is singly connected.

The proximity of the strike will also affect how damaged something is.

I live in a row of houses, and a few years ago, one house was struck by lightning. They had to be rewired, cables had blown through the walls. Their neighbour's wiring was OK, but they lost every bit of electrical apparatus they owned. Their neighbour lost all electronic equipment, but clunky things like tumble driers and kettles survived. Their neighbour lost computer equipment, but TVs survived. I was next in line. My ADSL router died, but everything else survived.

I now run the phone line and the power for my ADSL through a surge protector. The antenna amplifiers are pretty small ticket items. I have computer backups on removable media, and insurance for the rest. It's not worth my while breaking all connections between electrical things every time there's a storm.