BuddyPress.org

I first came across WordPress about five years ago via my company website, WP was used as the CMS.
I then used WP for a few sites of my own with some success. I then used WordPress with Buddypress for a music label site next-steep learning curve on that one.
I now use WP as a prototyping tool for experiments – the latest being http://www.acappellewest.net/Accendo which is a demonstrator site for an online design service. Note this one is a quick and dirty site so it uses the Parkour theme rather than a custom theme.
I view WP as a great CMS engine with an excellent range of plugins and tools that help me prototype new web experiences, tools and applications.