I understand. I am a web developer and am worried about using features of MySQL 5 in a project I am working on. Most of the users of my product will use them on a shared hosting server. I am worried I will exclude a huge section of the audience because of the MySQL 5 adoption problem.
I've seen mysql 5.0 mostly used recently, except older servers that have no reason to upgrade due to no development going on and they rely on old code and don't need features of mysql 5.0, those still run mysql 4. mysql 5.1 is used less, also due to major distributions not including it as default server yet.