I have been installing/using the latest Windows 7 RC build (7100) on a couple of machines over the past few weeks and I must say this build is very stable.  It fixes a number of issues over the previous beta.

1. Daemon Tools runs fine even though it throws a program compatibility warning.
2. Another guy also mentioned that it also fixed a number of black screen issues with Virtual PC 2007 SP1.
3. Copying large files over a network also now works.  It used to blue screen the beta.
4. The intermittent wireless dropping issues have also been solved.  The beta sometimes dropped my connections or sometimes lost my wireless settings.

 So far I have started using this in place of my original vista work machine and I must say that the stability and performance is great.  My current hardware also now responds a lot better with the new OS and all the applications that I commonly use are running fine.

Examples:

• Copying and renaming video files doesn't keep prompting me to retry (Vista had the issue where it was creating the thumb nail preview and it locked up the file)
• Starting up a VPC doesn't hang up my other applications.  I tried running a backup of my disk and outlook and then started a VPC.  My outlook was still responsive.  This had a tendency to blue screen in Vista due to the I/O load.

 The RC expires in June 2010 so I'll probably stick with this until the actual RTM comes in Oct 2009 (Rumoured).

In case you are wondering why Windows 7 seems so much zippier than Vista.  This article does an indepth dive of what was re-architectured to improve performance.  Interesting read.

http://blogs.msdn.com/e7/archive/2009/04/25/engineering-windows-7-for-graphics-performance.aspx

Productivity Tips (updated)

Here are some Windows 7 specific productivity tips I have gleaned so far (from testing and from other users).  I'll update this section as I find out more.

1. You can use the <Windows Key> and the number to bring up the application.  e.g. <Windows Key> + 1 brings up IE.  Holding the <Windows Key> and pressing the number again will normally cycle through the various instances.  e.g. For IE, it will cycle through the tabs.  I also noticed that if you change your taskbar to show the icons with text, the behavior will change.  It will bring up the application and minimize the application on the second key press.
2. <Windows Key> + <Shift> + [Number] launches a new instance of the application on your taskbar.
3. <Windows Key> + <Alt> + [Number] launches the context menu for the application on your taskbar.  i.e. similar to a right click.
4. Right click on the Explorer icon on the taskbar and you can access your frequently used folders.  You have the option to pin them to keep them on the menu.  Another cool thing is that you can drag any folder or network share link to the Explorer icon and it will create a pinned link for you.  Very useful to access your commonly used local folders or network shares.
5. Same as the above, you can add and pin internet URL links by dragging them to the IE icon.  This gives you a quick way to access common web sites by right clicking on the IE icon. The nice thing is that launching multiple sites will open up new tabs in the same IE instance.  Cool!
6. Note that for 4 and 5, the jumplist feature works for most other applications as well (at least for the recently used documents).  e.g. Word, Excel, PowerPoint, Media Player, Notepad, etc.
7. Note that jumplist features can be accessed by right clicking or even by holding down the left button and dragging up.  Cool!
8. Windows Live Messenger appears in the task bar when installed.  Some people don't like this and I prefer the old behaviour which was to appear in the notifications pane.  You can change this easily by modifying the properties of the msnmsgr.exe file under C:\Program Files\Windows Live\Messenger.  Select the Compatibility tab and then run it in Vista compatibility mode.  The next time you start up Messenger, it will revert back to the original behavior.
9. Notice that the icons a green progress bar for most of the in-built windows functions. e.g. Downloading a file using IE, copying a file over the network, doing a system backup.  Pretty nice visual indicator.
10. [Updated 19th May] I discovered that when a window is maximized, just dragging the top window bar will "auto-unsnap" the window.  Dragging it to another monitor and letting go will cause the window to snap back (i.e. maximized) to the other monitor.  This is really useful when dragging windows across multi-monitors.  You used to have to click the restore button before you could move the window.  You can also snap to half of the window by dragging it to the side.  Useful for viewing documents side by side.
11. [Updated 19th May] I heard news that the new Office 2010 will integrate natively into the Windows 7 task bar.  e.g. for Outlook 2010, you can right click and launch your inbox, calendar, etc direct from the Outlook icon.
12. [Updated 21st May] Saw this cool tip on Lifehacker where you can set the default printer based on which network you are connected to.  Very useful for laptop users who might have a certain printer at the office and another printer at home.  Access the settings from Control Panel -> View devices and printers.  Click on any printer device icon and then click on "Manage default printers" when it appears on the toolbar.
13. [Updated 16th June] Discovered that you can vertically snap the window by first hovering you mouse to the top or bottom edge until you see the sizing arrow icon.  Double click your mouse or drag it to the top/bottom edge and it will snap the top and bottom to the limit of your window.  Cool!
14. [Updated 18th June] Discovered you can create a new folder in explorer by just using the hotkey <Ctrl> + <Shift> + 'N'.  You can also immediately enter the new folder name at this point.  Very nice!
15. [Updated 19th June] Saw a tip on creating a shortcut for a new email.  Just create a new shortcut and specify "mailto:" in the location field.  You can even drag this into your Outlook tasbar icon and it will get pinned in the context menu.  This allows me to directly create a new email using the default email client.

Encountered Issues 

1. I initially had difficulty getting my fingerprint scanner to work.  It recognized the fingerprint scanner hardware and installed the correct driver.  I also registered my fingerprints using the default biometric tools in Windows 7.  However, whenever I tried to use my fingerprint to logon, it kept saying that there was no match in the database.  [Updated - Strangely enough I just tried it again today and it worked.  Go figure.]
2. Virtual PC 2007 SP1 - When my system memory is low, my running virtual machine sometimes loses the ability to click.  One of my guys reported that it also sometimes affects the keyboard key strokes as well.  The only way to solve this is to save state all running machines and close/re-open Virtual PC.