Why is a standalone 10Mbps network with 10-20 200MHz PCs, running NT4 on 64MB RAM, able to outperform much larger networks with state of the art Windows XP machines? Well, it surely outperforms the systems of many larger organizations if you want to run a normal database application with a good server.
Thinking of it, it does make sense: Modern desktop CPUs are not the bottleneck any more, harddisk seek time has not improved significantly and without other applications and network traffic, 10Mbps LAN is faster and more stable than many WANs - it surely has a lower latency because of the geographic limit. Also, Windows XP (and Vista?) haven't introduced anything really revolutionary with regard to speed, so the bottleneck in many systems is really the latency on the WAN.
Conclusion: For some GUI applications, performance was not improved by the improvements in desktop PC performance during the last 10 years, because network latency is the most important performance bottleneck.