I've used WordPress for a few years now, however, only the last year have I actually done any development relating to WordPress. I started back in December (2010) doing actual development for my work's website in WordPress. I was completely new at the time and haven't really done much PHP before that point. I worked on the project and got it to a stable-ish Alpha, but my work wasn't ready to make the switch yet to WordPress so the project got shelved for a year. I haven't really touched WordPress since then until February 2012 when a coworker presented a template he had done at the end of 2011 for work.
When I picked WP back up, I decided to re-invest time in my website(s), using wordpress as the primary CMS. However, I was disappointed at the lack of plugin support for themes. Plugins were doing some crazy stuff and hacks for their plugins to work. This prompted me to start writing a plugin of my own to make plugin developers have an easier time.
I intend on writing a series of about 20 plugins for WordPress, all depending on my one master plugin to synchronize things between themes, etc.