> What other serious drawbacks do they have?

They tend to rest on the plug's back, and hurt a lot when you step on them.

> Any other countries use them?

India and South Africa use the so-called Type D plug[0] (also called Type M in its 15A incarnation), which is similar but uses round plugs (type D is actually an older english standard). Some other south-east asian countries also use Type D. The english plug is called "Type G" and used in a number of former colonies and protectorates[1], especially in Africa and the Middle East.

[0] http://en.wikipedia.org/wiki/AC_power_plugs_and_sockets#Type...

[1] http://en.wikipedia.org/wiki/AC_power_plugs_and_sockets#Type...

Since you're calling it the English plug, I should mention that they also use it in Wales, Northern Ireland, and Scotland.

Ireland also use them.

I think that Singapore use the same plug.

Hong Kong sometimes too.