Two memories in particular stand out, one hardware and one software.
When the first dual core Athlon 64 chips appeared I wanted to go to multi core, but AMD was so far ahead that they were super expensive. Instead of going Athlon 64 X2 I bought a workstation board with two Nocona core Xeon processors instead - basically 3 GHz Pentium 4 with hyperthreading. Two core four thread goodness. I went AMD X2 later, and it was faster than the Xeons in a straight line, but felt much less snappy.
As for the software side, I will forever remember the day I upgraded my Pentium 3 machine from Windows 98SE to Windows 2000. I was doing a lot of web design and I could easily end up having to reboot 98 every hour or so. After I switched to Windows 2000 I literally went over a month without rebooting. That was the birth of the modern PC to me.