I have been using Vista for quite a while now. On the early betas I had my fair share of problems, especially since I was also running the early betas of Office at the same time.
In my job I do a lot of work in Virtual PCs ... these can be memory hungry things! For example one VPC I run I like to give about 1400Mb of RAM. My laptop has 2Gb of RAM. This works pretty well ... VPCs are a little slow to start ... but once up and running are pretty good.
Anyway, Vista has a great new feature called Windows ReadyBoost.
Adding system memory (RAM) is often the best way to improve your PC's performance. More memory means applications can run without needing to access the hard drive. However, upgrading memory is not always easy. You need to know what type of memory you need, purchase the memory, and open your computer to install the memory—which sometimes can invalidate your support agreement. Also, some machines have limited memory expansion capabilities, preventing you from adding RAM even if you are willing to do so.
Windows Vista introduces a new concept in adding memory to a system. Windows ReadyBoost lets users use a removable flash memory device, such as a USB thumb drive, to improve system performance without opening the box. Windows ReadyBoost can improve system performance because it can retrieve data kept on the flash memory more quickly than it can retrieve data kept on the hard disk, decreasing the time you need to wait for your PC to respond. Combined with SuperFetch technology, this can help drive impressive improvements in system responsiveness.
Windows ReadyBoost technology is reliable and provides protection of the data stored on your device. You can remove the memory device at any time without any loss of data or negative impact to the system; however, if you remove the device, your performance returns to the level you experienced without the device. Additionally, data on the removable memory device is encrypted to help prevent inappropriate access to data when the device is removed." - http://www.microsoft.com/windowsvista/features/foreveryone/performance.mspx
So I decided I would give it a go. Went and bought a nice and fast 4 GB SD card (150x, 22.5Mb Read, 12.5Mb Write) and put it in my laptop.
A dialog popped up asking if I would like to use this card to help speed up my system... I said yes. Another dialog popped up asking how much of the card I would like to reserve for Ready Boost. I choose 3.8 GB (it recommended that much). When I clicked OK the CPU jumped in usage for a couple of mins. I think this was it sorting out what to put on the SD.
After running with this turned on for a couple of hours now I can honestly say my laptop is much snappier when running a hefty VPC.
I don't think I will notice any difference when not running really memory heavy applications as my laptop has plenty of RAM ... but for running VPCs etc... it seems really good. The card was less than $80 USD ... a pretty cheap price to pay IMHO for an easier life running VPCs (my bread and butter).