I recently replaced this with M315 which was also good.
a) This model, newest as of now, has better wheel to navigate the page scroll than M315 which was a disaster if you were to scroll up and down the pages through the wheel. Its wheel is grooved more so than one in M315. Thus, giving a faster scroll on page up and down. However, it is still not fast enough to scroll quickly: If you have to go down 50 pages on your monitor screen, then you might still be better to use your screen scroll for quicker scroll than with this mouse. I am liking it better than M315 because I could use for scrolling at least a number of pages quicker-I could never use M315 for scrolling even few pages up and down.
b) Also, the wheel is better quality than the one on M315 which was very cheap quality. When you scroll with this wheel, it almost never misses "the beat" in scrolling. As opposed to M315 that would miss several beats easily when turning the wheel, especially when fast.
c) One major negative for me is that it is heavy. I mean considerably heavier than M315, some due to its two AA batteries. Thus, when I move cursor, I can feel the drain on my hand. M315 was much better in that respect. Also, this one is larger in size than M315. I actually liked M315 in that respect-though smaller, it was no big deal-you get used to it.
d) On the same note, if you used any photoshop pencil tool using M315, then the movement, due to its light weight, were so free that you could not make sharp and controlled movement that required tiny manupulation. In that sense, this heavier M525 is better for those who would use it for fine photofinishing tool etc.
e) Another bad for both mice is that the middle wheel scrolling for pages up and down is never smooth. When you use the wheels to go up and down pages, you will see it is not smooth and the page moves in "jerks."
Also note that it says batteries last for 3 years compared to one for M315 that would last for 1 year is due to the fact that this one takes up 2 batteries instead of one in M315. Thus, the battery duration (depending on use anyway) should not even be counted if you want to make a decision between the two.
Above were just negative. On positive side,
i) both mice worked fast and accurately without any delays or lagging at all. I mean no lagging at all even after sleep.
ii) Amazingly enough, this mouse worked from at least 10 feet away with the same sharpness and accuracy as if it were just close. I had hit my room wall, so it might even work from farther distance without any lagging.
iii) Even more amazingly, this mouse works even with that long distance no matter what direction the mouse faces and even if it is blocked with my body or some other stuff such as blankets in the room. It has worked on all surfaces from smooth mouse pad to rough fur blanket surface.
So, if you dont mind the heaviness and need to use for pages scrolling up and down with the wheel, then this is it.
If you dont need scrolling pages up and down with mouse, then I would go for M315 because it was lighter, smaller and did not tire my hands so much; the cursor response I felt was quicker and faster from one side of computer screen to another.
a) this mouse is heavier resulting in more energy to move and thus takes little longer to move cursor from one side of screen to another, and
b) that the page scroll is still not that fast, and
c) that the page scroll is not smooth but jerky with the wheel
I would give it 4 rather than 5.