I spent about a decade, from 1995-2005, building my own PC's, constantly upgrading, eventually putting all of the left overs together for another PC for the kids, and over time, would sell or upgrade more PC's. It was a good way to tinker around with the electronics, and kinda pay the way for the upgrades.
I never had any issues with the hardware, as mentioned in a post above, the only issues I ever came across was with the software, which could consume way more time than the actual build.
After laptops became more powerful, I moved away from the desktop PC, eventually moving onto the Apple platform for personal use. Absolutely love my MacBook Pro with retina display.
My 19 year old son told me last week he wanted to build a desktop for gaming, and I felt a stir within to perhaps join him on this journey. If he goes that route, I will only offer some guidance, as I would prefer he learn from the experience, rather than watch me put it all together.