I used to build my own, because that was the best way to get the specs I wanted at a good price. Especially since I run Linux. But I'm a software guy, and have always considered futzing with the hardware to be a necessary evil, rather than a goal on its own. Once I was able to get off-the-shelf machines that met my needs, I happily stopped building my own.
I voted 6-8 years ago, because the machine I bought about eight years ago needed some additions and improvements. It wasn't a full DIY, so I'm not sure it counts, but it was the last machine I had that was even partly DIY. Since then, it's seemed like machines that meet my specs are actually cheaper than buying their component parts, and that's before you factor in build time.