Why would anyone want to install a new operating system unless one had to? For us as professional developers it is to stay current and to help advise you. Or we run into the same kinds of issues you do - a new machine or a machine so screwed up that an operating system reinstall is the next logical troubleshooting step.
I found that on my home machine certain web applications were not running properly and they seemed to slow my browser down to a crawl. Since I have several other nearly identical machines that were running fine, the OS seemded to be the only answer. Uninstalling and then reinstalling networking had not cleared the problem.
The Windows 7 (release candidate - the try it but don’t blame us if it doesn’t work version of the operating system) install directions of course warned me to back up my system and then do a fresh install (not upgrade) of the operating system. Because I wanted a clean install the lack of an upgrade option was not too troubling. Note that a clean install will require that you reinstall your desired programs, although your data will be left intact. I needed to download the software and create an install DVD which meant I also needed to download the latest version of a burner. The directions were all straightforward and easy to follow. The process took 4 to 6 hours from start to finish. I was somewhat confused as the install of the OS did seem to offer an upgrade option.
Windows 7 looks more like Windows Server 2008 than it does like Vista. I found the Vista interface to be confusing and too cute. We only installed Vista on some of our machines to have the environment available for testing. We did in fact do more Vista uninstalls for customers than we did installs!
Windows 7 required no real learning - everything is quite intuitive. I did find that there is a machine tuning utility that lets you determine the machine componenets that might be slowing down overall perormance of your system. There is even a way to turn off several graphics features if your graphics card is the weak link in your system - it was in mine.
Task switching seems to be a little faster. I also found that squences that previously hung my browser were now able to be automatically worked around by the OS. That was a real plus. The additional features that let you see or preview more of what you are doing are not yet something I hae come to appreciate. I assume I will find more use for them over time.
I did find that the install set my monitor to the highest resolution available which I needed to dial back as my eyes no longer acoomodate that resolution well.
But all in all I would recommend and suggest that an upgrade to Windows 7 should be painless.
I did remember to save my Outlook data to a pst file so I could recover it easily. I forgot to save my browser favorites but they were still accessible after the Windows 7 install.
BTW - the install did clear my web browser application issues.