I installed Windows 7 RC x64 on my second drive and it's pretty solid. Really solid. See my last post on the subject for thoughts on running the beta. The RC is something I might consider running full time.
For one thing, it's faster and installed even less painfully than the beta. The Windows install process has improved a lot since XP (the Vista install was pretty good, albeit slow). Win 7 installs somewhat faster. The built-in driver support is also spectacular. My machine was up and running perfectly with no additional drivers (in fact, an Intel driver bug I know of made it into this release).
The OS itself is faster than Vista on the same machine. Granted, this is a fresh install, though I’ve put a bunch of apps on already and it continues to perform great. I’m a huge fan of the Windows-key-to-search shortcut in Vista. I use it for everything. It’s much, much faster than Vista’s, even on a bare install.
I've been very skeptical of the new taskbar, but, I've come around to it because the right-clicking features are really nice. The addition to right-click features for the control panel is very welcome. They've changed the highlighting so apps that need attention now actually get my attention (this was a problem in the beta). Also there's a little bit better delineation between apps that are open with multiple windows and apps that are closed.
They changed some icons, for the better, I think. Remote Desktop Connection doesn't look like "My Computer" as it did in earlier versions. The new sound themes are nice. I’m using the “cityscape” theme. Maybe I can get used to one of these so the Bank of American ATMs that use old default Windows sounds won’t annoy the crap out of me thinking there are constant errors while I’m getting cash out.
The new Media Center is great. For one thing, you can finally drag the current position on the timeline. This was probably the #1 thing I felt was missing from media center previously. They also made it so you can add your ripped DVDs without having to do some registry hacking to get it to show up. The performance in a window seems better as well. I'm typing this with "Cloverfield" playing (ripped DVD), a few apps open and the machine is having no problems keeping up the playback.
I’m still unclear where Media Center is going though. It’s pretty much the best software that comes with Windows that no one will use.
HomeGroup seems like a great feature, and you can share media with your homegroup over Windows Live now in the RC. I’d love to try this feature out more, but I’m not willing to install Windows 7 on multiple machines as of yet.
UAC is less invasive for daily installs and usage.
Apparently Microsoft is adding a built-in XP virtual machine for Enterprise, Business and Ultimate versions of Windows 7. This was a secret feature until Paul Thurott revealed it yesterday, and it sounds like a really good move on Microsoft’s part. Obviously it won’t work for the business that I’m in, which requires DirectX and OpenGL, but I’m sure it will help the business adoption of Windows 7 overall. It’s a bit like the move that Apple made with Mac OS Classic for MacOS X. It might be so slow performance wise that it’s unusable, but hey, it will get a lot of people to upgrade who otherwise wouldn’t.
Anyway – Windows 7, I’m running it to type this. We’ll see if I continue to run it in the days and weeks to come, but I think it’s a given now that I’ll upgrade on day one of the RTM
 – For those who know my tendency to early adopt, I did not run the RTM of Vista on my main machine at home for at least 6 months (it was a new machine), and at work for 2 years. I expect that timeframe to be much, much shorter for both locations for Windows 7.