Okay, this probably won’t be what you think (I am misleading you just a little by the title here), but if you want to see a significant increase in performance from Vista, I suggest switching to Server 08 as your workstation. Many administrators prefer to use a server based OS as their primary workstation for several reasons, one of which has not been performance. This all changes with the modular design and function of Server 08.
After almost a year of running Vista in a production environment and dealing with what I felt to be major performance pitfalls, I resolved to install Server 08 as my primary desktop. First, let me explain some of the performance issues that I was seeing with Vista. My primary work machine is a Dell Optiplex GX270, 3.2GHZ and 2GB RAM, which ran XP at a blaze. Upon installing Vista, the painful three to five second delay in program launch (and yes this was before adding AV) could be felt almost immediately, but because I really wanted to learn the new OS, I dealt with it. I would often have applications hang, or they would be extremely slow to respond. Such was the deal when working within the GPMC or ADUC. On average, I would need to reboot Vista about once per week just to gain some performance back.
A coworker of mine decided to test out Server 08 on his MacBook and I watched as he launched app after app without any slowness. I decided to wipe Vista and give Server 08 a try since the GUI’s are pretty much identical. In order to clean up some of the Server 08 nuisances, I followed the tips at http://www.win2008workstation.com which really helped. I have been running Server 08 for about a month now and have not had to reboot it since first updating it. I notice no slowdown of apps and application launch is usually under one second, a far cry from Vista. There is a lot of information on the net regarding the use of Server 08 as a workstation and my personal experience just adds to the fodder. So far Server 08 appears to be rock solid, and more time may dissuade my high opinion, but for now I am very content!