After extensive testing I found the IE4 to be comfortable, responsive, and extremely accurate. I have not said anything about the 800 dpi optical sensor so far but it suffices to say that the IE4's works flawlessly on any surface I could fine. The only sensor that can match it is Logitech's acclaimed MX series.
This mouse is a solid purchase, there is not much more to say... I think that the retail price of $39.95 is a bit high but thats how it is. Past that, so long as you are willing to customize the mouse functions and can deal with a smooth scrolling wheel this mouse would be a good pickup. I am glad to see that some company, even if it has to be the big "M", is giving Logitech some competition in the peripherals market. This is a great alternative, finally.
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