Ok first i must intro myself so you know the limitations of my review. I HATE Microsoft mice. IE 3 or 1.1. they dont suit me at all. IE3 is too big and 1.1 is hard for me to lift. I play cs with my wrist - alot of small turns. Before i bought the IE 4, the mouse that best fit me was the logitech 1st mouse (scroll), mx300 + mx500. I wont bother comparing with the mx310 as many have told me that the laser is different from 300 + 500 becos u have to lift it much higher from the pad for the laser to stop tracking.I have asian hands btw :P
SHAPE
From the pics you can see that IE 4 is slightly bigger than the 1.1 and mx300. it is slightly shorter in length vs the IE 3. This is good for me. IE 4 has a wider base breath and this makes it very stable. The thumb cavity and resting spot for ring and little finger (black sides) are much more comfortable then IE3. The way my thumb and last 2 fingers naturally positions grabs the mouse very well and makes small turns/flicks a breeze to execute. Much better grip than mx300 and mx500 and 100 times better than 1.1. I find the mx500's right hand side rest painfull on my last 2 fingers, if any1 has the same prob, this mouse is your saviour.
Also note the prominant curvature of the top leading to the 2 main buttons. It feels even more comfy than it looks! This plus the arch / dome of the IE4 makes it more comfy than any other mice i've used for my palm to "cup". IE3,1.1,mx300&500
WEIGHT
Its light. I didnt weight it but just based on holding it. It is around the same as 1.1. Lighter than a mx300 (with weight removed). Even though some people think that too light isnt good for aim ( i agree ), i feel that the balanced shape and broadness of the IE4 throws that "rule" outta the window. Its great for wrist players like myself.
BUTTONS
By this i mean the position of the buttons plus how nice the clicking is. The 2 main buttons are great- perfect even. Nice click that is not too bouncy/spacey and has good depressed contact But i found the side 2 buttons too far from my thumb to press. When my thumb does press the side buttons, all grip needed to move or lift the mice is gone. The wheels, scrolls without clicking/stepping (if u know what i mean - totally smooth) so I cant tell how many my feel how deep into inventory i've gone in cs (i.e. HE or Smoke gren) unless i look at the hud. I dont like this. However, the wheel button is nice to depress unlike the other mice and accidental scrolling while depressing wont happen .
FEET and LASER
The feet are exactly like the optical blue and other new generation MS optical mice - i.e smaller then ie3 / 1.1. Same black material that has shit feel on any surface. Hard pads are gonna get owned. Laser : so far nothing on the MS website about improved scanning rates or DPI. Box it came in also doesnt state its optical capabilities. So its safe to say its the same as Ie3 / 1.1. I for one cant tell the diff between logitech's higher refresh rate and 800DPI vs this mouse because i didnt test them side by side plus logitech work nicest for me with MS drivers.
CONCLUSION
BEST MOUSE I'VE EVER TRIED for years.Would be perfect if not for the 2 side buttons and non-clicking scroll wheel + gay feet that forces you to use skates. To be able to convert a loyal logitech user and microsoft hater takes something special. The IE 4 has it all. Alot of players dont wanna change mouse because they think "Hey, im good with this, comfy and all.. it aint broke why fix it?". Well my reason is that some times something comes along that blows the rest outta the way. I've never found a better feeling mouse than the logitech first wheel mouse until the IE4.0.