With the public beta of Windows 7 in full swing many people are talking about performance and comparing different versions of Windows. I see many posts in forums and on newsgroups exclaiming Windows 7 boots x seconds faster than Vista. They carefully measure how long XP, Vista, and Windows 7 take to boot or shutdown. Others measure how much RAM each OS uses when at idle. Some people run benchmark software comparing various OS's. There are web sites dedicated to performance with tips on which services and scheduled tasks can be disabled to improve performance.
Most users are more concerned with perceived performance rather than actual performance. If I click on something is there a pause before something happens? If that pause is longer than x (I don't know what x is but I suspect it's less than a second) the computer or application is perceived as slow. If it's faster than x then the computer or application is perceived as fast. There isn't really any in between. There is no perception of medium performance for most people. It's either acceptable or too slow. Most current operating systems take all this into account and are optimized to give a good user experience. Sometimes this perceived better performance comes at the expense of actual performance. The operating system is doing things in the background like indexing files, optimizing the file system, pre-caching disk sectors, and more. These background tasks may cause benchmarks to run slower. Some people jump on this and disable these background tasks then proudly post benchmarks proving how much faster their computer is. The problem is that disabling these background tasks quite often makes the computer less optimized for the user experience. Programs may actually run slightly faster but loading the program or loading/saving files from within the program take longer. Finding the email you sent to Joe Smith about next week's hockey game takes impossibly long as you have to manually open each email. Over time Windows slows down because the disk is fragmented.
When tuning or measuring computer performance you have to take many things into consideration. It's very similar to a car. Most of us don't want to drive a souped up hotrod that's temperamental and needs constant attention. Most us want a car that starts up when we turn the key. The heat or the air conditioning comes on quickly not several miles down the road. We want power locks, windows and seats. We want comfort. It's the same with computers. There are enthusiasts who enjoy eaking out every millisecond of performance and don't care about the comforts or ease of use. Unfortunately many people listen to their advice and think that if they apply the same tricks their computer will be faster. It will, but the catch-22 is that their day to day computing may actually seem slower.