So let's get started, shall we?

1. Design - 9.5/10
The Sidewinder has a quite exceptional design. It doesn't look too complicated, yet it is very visually pleasing, with the exhaust pipe-like thumb buttons and the lights trailing off the rear end.
The thumb buttons are located in the perfect spot to make them comfortable to use, and the vertical positioning of them makes them nice to rest your thumb on and easy to tell which is which. I find that they also designed them well enough that you can press them easily when you mean to, but I haven't accidentally pressed one yet.
The LED display is positioned between your thumb and first finger, and it's at the exact right angle to see it without having to move your head to look.
The only problem I have with the design is that the three buttons for "On-the-fly DPI switching" are placed in such a spot that, while it's still quick and very handy, however it does require moving one of your fingers - and a quick glance - to activate them.
2. Features - 10/10
I am incredibly impressed with both the numbers, and the quality of the features on this mouse.
The buttons on the mouse are expertly placed (aside from the DPI switching buttons), and the metal scroll wheel feels nice, works well, and is smooth to use.
The Sidewinder logo button that hides under your palm is well-designed. You'll never push it by mistake with your palm, and when pressed, it takes you to the "Games" folder of Windows. I'm not yet sure how to change that to bring up your mouse settings.

The custom weighting system is very cool. I was surprised at the differences it makes, and very quickly found the right weight for me. The tray stays in and won't get knocked out, and the release button on the bottom for it won't get pushed by mistake either. Excellently done.

The custom 'feet' allows you to control how easily the mouse slides across a surface. But it doesn't stop there - I set mine up to be easier to pivot (because I play a lot of First-Person Shooters), by placing the white one (least 'slippery') on the furthermost spot toward the back, followed by two gray ones (mid-slip) on the two in the center, and finally two black ones (the most 'slippery') as the front two. This increased my accuracy a surprising amount!


The mouse also comes with a small black box that serves as a storage unit for the spare 'feet' and weights. But that's not all - it serves a double function as a nice, hefty cable anchor! This also impressed me a lot.
The LED display is perfect for seeing the DPI setting you're on, as well as knowing that the macro recording is on, or the Quick Turn calibration is activated. It's an incredibly handy feature. I love it!
The macro-record button is also really cool, and really handy for the macro-users, however I don't have much to say about it, because I never use macros. (I find that it spoils the game.)
Software-wise, there's a long list of functions available for assignment, so you definitely won't be disappointed there. I'd like to point out four specific ones from that list (Which I don't have screenshots for yet, so please bear with my descriptions until I have a chance to edit the post and add screenshots!)
1. Quick Turn
This was especially impressive to me. It's really for players of First-Person games. Here's how it works: You assign the function to a button. Then, once you're in-game and set to the DPI setting you'll be on when you use this function, you hold down the button (at which point the LED display will let you know it's activated), then turn your character a full 360-degree turn. Let the button up after that. Then, when you press that button, your character will quickly spin around approximately 180 degrees (Not precisely, because that would make the advantage too great). This is perfect for quick, reflex moments! I love using it. :)
2. 3D Flip
3D Flip was the name given to the Windows 7 function that occurs when you hold the windows key, then press tab. It brings up a 3D list of panels depicting the windows you have open. Continuing to hold tab, you can then flip through. With the feature assigned to a button on the mouse, you can pres it once and the list stays up, then you can scroll through the list with the scroll wheel. I have it set to activate when I press the scroll wheel down.
3. Magnifier
I had the magnifier set up as the thumb button on my previous mouse, but it appears that the software for the Sidewinder enhances this magnifier. Aside from its regular functions, this magnifier, when already activated by a push of the assigned button, will allow you to move the mouse horizontally or vertically to adjust the size of the magnifier 'lens' if you hold the assigned button down. This made me smile when I discovered it.
4. Button Profiles
You can program your buttons to do one thing in one program, another thing in another program, and something different normally! When a program is open, the profile for it kicks in and it changes, so if you set the Magnifier to the top thumb button in normal mode, when you open Call of Duty, it won't conflict with having the melee attack set to the same button (Which I find it does. In-came hotkeys don't like when the magnifier is set to the same button, because the magnifier doesn't open when something full-screen is running.)
Function - 9/10
While I would like a wider range of DPI settings available, the mouse is very responsive, accurate, and all the functions work smoothly. The design is comfortable to my hand as well.
Price - 8.9/10
Despite how much less expensive it is than something in the Razer line of mice, $80-90 always seems like a lot to shell out for a mouse. But in my opinion, it's definitely worth it!
Overall - 9.8/10
I love this mouse, and I will never regret purchasing it. It's accurate, responsive, feature-packed, and excellently customizable. The Microsoft Sidewinder has changed how I game in some great ways. I love it!!
-Grynder