I haven't used it but have read some good things about it. One of the advantages over other CMSs is that it is gentler on server resources as it doesn't use a database - it uses XML to store data. You may google it for other features.
I haven't used it myself, but heard some great things about it a few months back from one of the people that helped out with it's development testing.
I heard about the resources advantages that you said as well. I had plans to test it out on a site, just to see for myself. Just been too busy to get around to it lately.
I am planning on doing it after the 1st of the year sometime.
Never heard of it either. Sounds interesting. Though I don't know if I like the idea of it not using a database. I am not an IT pro, but seems as static files get bigger, would take more time on the system? Just seems a DB would be quicker as a site grows?
As Harry said, it's hard to beat all the plug-in's, theme's, resources and help you can get with Wordpress.