This plugin was easy to install even for a novice like myself.
Configuring the plugin is simple, because you can just add the two letter country codes instead of IP ranges.
It works perfectly (I tested it for my own country) and I have not noticed any incompatibility issues.
The developer responded quickly to my inquiry.
In the future it would be nice to be able to block back-end admin interface also and see somekind of statistics of blocked attempts.