I read about it when I first started out, but I didn't think it was anything special (boy, was I wrong)
Then I was given a website made in MODx at work to fix, so I had to learn it on the job. Loved it!
one of my good friends, who is also a web designer told me about modx - I did not try it out immediately but after a couple months I thought I might give it a try
I've discovered it thanks to my brother who used it before.