First off, i want to say I'm thankful that Logitech provided an overdue update to the wireless trackball. Thats great. But why in the world wouldn't Logitech ship it with their new-great technology Hyper-Fast Scroll Wheels? I mean, it just seems like a huge blunder on their part. Someone their needs to be talked to for making that call. I could have easily plunked down a few more bucks for it. And it makes the M570 already out of date. I just wrote a review for the mouse for those interested. Scroll Wheel rant is in BOLD ITALIC
Almost Perfect:
I waiting a long time for this trackball. I had the wireless version with the huge receiver and I literally used it to the point that the base plastic was showing through. I also broke the scroll spring. You can say I loved it to death! As annoying as that huge receiver was, I hauled with my laptop when on the road, and had it on my desk when I settled on the desktop.
The new M570 seems almost perfect because thats how I feel everything about it is.
Materials: Well I don't care for heavy material, and knowing that my older model laster for so long, (2001-2010) I'm not too concerned as I really made that little guy pay for itself. In bags, boxes, it fell a few times and only broke the spring the last year of use. The materials in the new one don't feel any different. light, cheap, but seem to be durable. I'm for it. Maybe it could have been built with better material, and that would have been perfect.
Design: I love the design, and I don't mind the little curviness in the newer design, but the minor issue is that its a tad smaller. While thats not a HUGE deal, I'd prefer the slightly bigger size. My hand fit better on it.
Trackball Smoothness: I read a number of reviews on how the new blue is slow and had drag so I even popped the red ball out and got it cleaned to pop it in place of the blue. It literally took me an hour or so and the blue ball was as smooth and great. I have no complains here.
Battery Indicator: Simple, and understandable. Great to have around. Aesthetically, I would have dropped the battery logo! 
Unified receiver: Perfect, what would make it more perfect? perhaps not having it. Or having an option to use BT or Wireless to sync. But Its 1000% better than that ridiculous receiver had before.
Extra 2 buttons: Great addition since we didn't have an option before, but the location is not ideal. I don't use them at all. Then again I don't like to move my fingers too much.
Scroll Wheel: This is the BIGGEST issue I have with this trackball. You have the hyper-fast scroll wheel on the other mice models, WHY OH WHY wouldn't you include it in this model? It boggles my mind. Is it price? I would have plunked an extra 20$ for that sucker. The hyper-fast scroll wheel is the best thing that happened to mice since the introduction of lasers. I wanted to break that Performance Mouse MX case and pull it out for my M570... if that would have worked. Not sure who on the Logitech team made that call, but they need to be sent to the corner for a good timeout. I would reconsider launching it with it, you have a technology which is superior to others on the market, why wouldn't you upgrade this most anticipated trackball in your product line??? Give me one good reason besides cost... I dare you.
Overall: A great product. I would have give it a full 5 star has it had the hyper-fast scroll in there. But it doesn't. So i didn't.
PS Man, I still can't get over the fact that you didn't have hyper-fast scroll on this thing. What a shame.
