Updated 8/31 - additions are in Blue for pro's and in red for the con's.
Updated 9/1 - Added a con in maroon
Version: Windows 8 Enterprise [MSDN]
Score: 8.5/10
I'm doing this off the top of my head. The fact is that Windows 8 is packed with new stuff and changes and I know I am going to forget things that should not be forgotten.
Pro's:
Start - The traditional start menu is gone, replaced by what I describe as a start "page". You click the very bottom left corner to invoke this page, and it has blocks on it. For example Desktop, Pictures, Music, News, Weather, Pinned Apps, etc. Once you get used to this it really rocks.
Blocks - The blocks are great. They launch "pages" that are integrated into the OS. For example when you click on "Weather" you get a "wall" that fills the entire screen and it gives you a background of the weather (sun for sunny, as an example), your five day forcast, and options like hourly breakdown run down the right side. The Music block works the same way, and you can "swipe" from left to right for different things like My Music, Now Playing, etc. It's so great having Weather, News, and Sports integrated in a seamless fashion right out of the box.
Pop out panels - You hover over the corners with a window of options. The right side gives you things like Settings, Search, Devices, Start, etc. Left bottom is the start menu. Left top shows you the last window and left middle shows all the apps / windows.
FAST - Windows 8 is the fastest Windows operating system I have ever seen, period.
Functional - I'm not bothered to make decisions constantly like when Vista launched. 7 bugged me some too. 8 knows what needs to be done and doesn't bug you with petty crap. All of my drivers were perfect out of the box, not a single generic driver. Network management is great and seamless.
Stability - Not a single error or crash in about 80 hours of actual use, no reboots in days. Actually I have not a single reboot that was required or needed.
WMP - Finally gone. They still have a player integrated for media but it's not WMP, and it's a move in the right direction.
Default Programs - The days of Windows bickering with third party software to be default are gone. In fact, MS has sort of embraced the third party market. For example I installed VLC, but I did not make it default right away because quite frankly, I may not even need it for most video files. Anyway I opened a video today that I downloaded and it opened in the default W8 player. Are you ready for this? On the right side a small box appears that says "You have other applications installed that can play this type of file, would you like to view the options?". Holy cow, Windows just asked me if I wanted to leave their default player to use a third party player. The video was playing fine, there was no reason to switch unless I simply wanted to. This SHOCKED me. Also, IE10 has not once reminded me that it is not my default and asked to be. Not once.
Personalization (is that a word?) options are great. Windows goes out of it's way to mold to you.
Control Panel - The new panel is great. They use the same style as they did with W7 but the links under the titles are actually useful now. It makes the control panel very streamline and intuitive and allows you as a user to find what you need very quickly by placing the most common adjustments right up front.
Credentials Manager - I'm really not sure how the security will be, only time will tell us that. But I can tell you the credentials manager works very well, it lacks the clunky nature of the previous attempts at this concept. It reminds me of Lastpass.
Windows Defender - It has a new name now I think, I'm not sure because it rarely bothers me. WD has made some vast improvements for real time protection. With Linux I never really gave a whoot for obvious reasons, but on Windows protection is key. There were some infected files in my data and WD found them on the fly, corrected the issue and - here is the impressive part - appeared to make no difference at all in the speed of completing the task I was doing. WD is completely hands off and functional.
Find - Typing the con for the app's reminded me that Find needs a pro. The search function in Windows 8 is now called Find, and it is lightyears beyond the previous system. Windows Key + F is the quickest way to open it, and when you do it is a "wall" like the other pages, and down the right side is a list such as "Apps, Settings, Files" and you click the one you want (or click nothing for a full search), type it in the box, and the whole page displays hits. The search is FAST. F....A....S.....T......FAST.
Hot Key Dialog - I like that when I turn up my volume or adjust my screen the pop up window is clickable with various options. For exmaple when I volume up I can also go forward or back or launch the player.
Con's:
No "X" button on a lot of windows. For example Chrome, IE, any of the integrated applications, etc. All they need is one to appear when you hover. You can right click and close, but come on give me the X. Library windows have them, as do most applications you install third party. This is becoming less of an issue the more I use the system. It seems to me the new setup is faster, you just need to shed the conventional Windows view. Windows 8 is clearly a step towards a touch screen friendly interface.
No Blu-Ray support. This was easily corrected but it's 2012, it should have native support.
Internet Explorer - Still BLOWS. No shock there though.
GUI is a bit touchy, so you want a slower mouse speed than you would normally have. What I'm using is pretty much the finalized Oct release so I wouldn't expect something like this to change, as it is not an issue for many people. It's not even for me really, but it can be a bit of a learning curve.
App Access - You really need to put some effort into getting this setup. For most people they probably won't notice because of desktop icons. Me I hate desktop icons and a cluttered task bar so this is more important. Take for example the calculator. You can't just click start and jump right to it anymore, you need to locate it. The fastest way (without pinning a shortcut) is to hit Windows Key + F, click on Apps, and type in calculator. Kind of annoying, but a small price to pay for the great new start page. Like I said common things you pin to start and/or taskbar and no worries.
I really wish I could swipe in the panels for things like Music. Going to the bottom to drag the scroll bar left and right is annoying. Give me a mouse gesture so I can swipe left and right like I do on my phone. Clearly that is the point, give all devices the option to do this.
I'm irritated that I have to go into the desktop background dialog and navigate to the folder containing the image I wish to use in order to change my background. When looking at an image you can right click to get a set as dialog but it only contains lock screen and app, no desktop background.
Overall Impression
Regardless of what OS you are currently running Windows 8 is undoubtedly going to be an improvement for you given your computer can support it. The con's are very minor and far outweighed by the pro's. Windows 8 is the most solid operating system I have ever used, runs incredibly fast, and really shows a huge step forward from Microsoft.
When the official release hits in October I will be purchasing a license and sticking with it.
Pictures added of Start....Weather...and Music so you can see what I mean by launching them gives you a "wall". You can see on Music where you can go the different directions side to side for more options.