Pros: - Reliable, especially for a wireless mouse. I've had this mouse for more than 5 years now. Still going (relatively) strong.
- Receiver is small enough to leave in the USB port of a laptop with no worry of catching on anything.

Cons: - No mouse wheel "click". This is problematic in some games and applications that set each scrolling "click" as another option.
- High scrolling sensitivity. This can be fixed in the control panel, but the lack of tactile and audible feedback for each "click" makes it easy to overshoot.
- Side button doesn't work 3/4 of the time in games, and may have weird behavior when used while typing. This may be a software/driver issue with Microsoft. I personally mapped it to forward slash for commands.
- Adhesive for rubberized side panels had started to wear through and come off around 3.5 years in.
- Mouse has been doing some double-clicking inadvertently recently, probably due to switch wear and tear.

Other Thoughts: - GET RECHARGEABLE AA BATTERIES. I can't tell you how much this has saved me in battery costs over the years. My best guess on battery life is 20-35 hours.

Long Term Maintenance:
- If the rubber mouse wheel part starts becoming loose, or if you don't like the mouse wheel having as much friction as it does, cut and remove the rubber. It's just a ring around the wheel. I actually prefer the bare plastic feel to the rubber.
- The rubberized side panels can be fixed by careful application of electrical tape, which is hand-friendly enough and closes tears and gaps with the side panels.

Ergonomics:
I have slightly large hands, so when I rest my wrist on my desk, my fingers just barely touch the desk on the other end of the mouse. Definitely a claw-grip for me.

I find I actually prefer the mouse with the above modifications, but maybe that's just me being sentimentally attached. There are more durable and longer-lasting options out there, but most either cost more or are wired. This is a solid option, especially for carrying with a laptop.

Pros: Great sensativity, feels good in your hand, light, works as well as a wired mouse

Cons: This mouse has a design problem: it began double-clicking about six months after the purchase.

Other Thoughts: I didn't buy this from NewEgg but I thought I'd comment anyway.

Pros: Tracking seems decent
Good size and mouse shell
Side button

Cons: Battery drain
RF distance, needs receiver within 6ft

Other Thoughts: I had to buy a usb extension to bring the usb RF receiver closer when I used the mouse greater than 6ft from my computer. Otherwise it would barely track and got really choppy. In comparion, my M505 is operational to more than 9ft from my computer. The battery also drains twice as fast as my M505.

Pros: The mouse feels great in hand and is very comfortable for a mobile mouse.

Cons: Only has the one extra button on the right thumb (usually used as a back button in a web browser) kind of wished it had two for forward and back.
It might just be me but I feel that the battery doesn't last as long now two years after purchase. I now get about 2 months of use working 8-5 m-f on a battery but dont really remember what it was when it was new.

Other Thoughts: The scroll wheel is continuous. After two years of use it is still working. Though over that time the wheel has probably gotten some dirt in it so it doesnt scroll as nice. I havent tried to open it and clean it yet. Also a few months ago the rubber that is around the wheel has come loose so it moves when I use the tilt function of the wheel. Other than that no issues with the mouse.

Pros: Good resolution for a non-gaming mouse.

Cons: Only one thumb button.
Goes through batteries faster than any of my other wireless mice (1xAA every other month).
The left button will not respond to clicks sometimes, while other times it registers a double-click. If it were only one or the other, that'd be fine, but it's supremely frustrating when it will arbitrarily switch between the two.
I use command-line programs the vast majority of the time, and I use a keyboard-navigation plugin for my webbrowser; I really don't use the mouse an awful lot. So if a guy like me can wear this thing out after 18 months, I can't imagine how quickly it must fall apart for an average PC user!

Other Thoughts: I was able to get used to its small size, but it just doesn't hold up to regular use.

Pros: Works well even without a mouse pad.

Cons: None

Other Thoughts: Great mouse. I love Microsoft Mice!

Pros: light weight, smooth and sleek design

Cons: battery that came with did NOT work for the time they state.. lasted about a month; however, rechargeable fit well.

I also ended up having to dismantle it and loosing the screws on the front side (under the mouse buttons) as the scroll wheel would seem to get "stuck" or rub at a particular point in rotation. Slightly loosing those two screws solved the problem... the person whom works at the factory was a bit zealous.

Other Thoughts: would like to see more models like this version.. fits my hands well and totally portable.

Pros: The mouse fits well into the palm and its shape is simply perfect for long hour working. It's a no-fuss great mouse.

Cons: The mouse started double-clicking on single click commands after about a year. I'm sorry, but that's unacceptable. This is a Microsoft product. I have higher standards for them.

Pros: None

Cons: The mouse is WAY too small and I have RMA for a refund.

Pros: Feels great in my hand, works on every surface i've needed to use it on.Very responsive and efficient device. On\Off switch is convenient way to save battery life (instead of having to pop out the battery after use) Just plug it in and it's ready to roll unless you're a real picky mouse aficionado and need to tweak every setting, go download the latest intellimouse software from Microsoft.

Cons: The scroll wheel is almost too sensitive\slippery with no tactile or feedback to it. Not a game changer as sensitivity can be adjusted but took a little getting use to.

Other Thoughts: I can't stand trackpad when it comes to work productivity on the go, a wireless mouse is the way to go and this one gets it right!