It's a closed system, so there's virtually no advertising, no spam, and almost no americans. Which isn't necessarily a bad thing, but when you want to talk about the latest Simpsons cartoon, for example, you'll be talking about different ones. Or Star Trek. Or, well, you know.
It started a long long time ago, and currently has around 10,000 members. I'm in the conference for Yorkshire, among other things, and we meet up every month to drink large amounts of beer and generally talk about nothing. Which is all quite nice.
To use CIX, you need a piece of software called "Ameol", which works much the same as an offline newsreader. You can read through the messages and reply without being on the phone constantly. CIX is also an internet service provider too.
There are also CIX readers for Psion computers, Palm OS, and you can even telnet into CIX and read it live over the net if you want to.
The author, james007, has been on CIX for really rather a long time.
Douglas Adams was also on CIX - his nickname was "dna".
CIX is pronounced "Kicks".