My first computer was an Apple IIe.
I remember when 512 MB of RAM was a lot, and 2 GB was an expensive luxury (close to $400 in 2003), but more RAM made XP Pro work better.
I remember when 80 GB of storage was huge.
Early builds were a crap shoot. Different components did not like to play well with each other. Functional drivers were often an issue. Now RAM is cheap. Components are truly plug and play. Cases are well made and highly functional.
I have built or help build at least a dozen computers in the past 15 years. My smart phone would destroy any of my early computers. However, as good as phones and tablets become, they cannot compete with the speed, quality, and versatility of a good PC. My newest PC with Windows 8.1 boots from an SSD with amazing speed. Most components get better and better. Hopefully the market for PC components and cool modding supplies will remain robust!