Logitech's recent performance has been anything but smooth. I dug up an old A4 on a cord when 603 started sounding utterly tinny with a double click. I don't remember how long ago it was. It is effective, and nobody has any complaints about it! Oh, if only there was a mouse that ran on AA batteries. Dreams. Has pros: AA batteries are fantastic in every way. If you use it once a day, two enelop'a on 2400MA/h should be sufficient for practically a whole year. Comfortable for big hands. Good sensor. fashionable and (still) recent. Con: The insignia that was supposed to be on the lid wore off after just one month of use. Plastic legs that staggered in length after only a half year of use - are you serious, Logitek? Do you think it's a waste to add aluminum legs in a mouse that costs $100? They even fit two sets on one side of an A4 sheet. And nothing, they did not end up going out of business. After another year and a half had passed, a double click started. And the further you go, the happier you'll be. At first, when I fell periodically, I assumed it was because my finger was fatigued or that it had a spasm. Now and then it only clicks twice, but the majority of the time it clicks twice. Sadness . A mouse purchased for one hundred dollars was sufficient for just over a year's time.