This is a very comfortable mouse! I didn't give it 5 stars because it's a tad big for my hands, which might just be a little smaller than average - but it always seemed to me it is harder for those with larger hands to find mice, so that's probably a good feature. It is still a big improvement! It has nice grip on the thumb side and a nice-feeling semi-rubberized right side (which I wish were a little more grippy). The scroll wheel has a very nice feel and grip. The nano receiver fits into the bottom fairly firmly. Completely plug and play on my MacOS10.8 setup. Tracks and slides nicely, feels quality all over. The DPI changing button is in a nice spot where you won't accidentally hit it, too. Great buy! 

Question: How is the button easy to press?
Answer: The nano receiver fits into the bottom fairly firmly