I gave this one a try when it went on sale last week for $39, my old/original Arc Mouse died after a few years of use.
This review is primarily a comparison between what I was use to with the original Arc Mouse (I'll just continue calling it Arc Mouse in this review), compared to this new Arc Touch Mouse (I'll continue calling it Touch Mouse).
The contour of the Arc Mouse was easier on my wrist, it had a nice curve to it. The Touch Mouse has a high curve around your palm area then slants straight to your fingers, this didn't feel comfortable to me.
The buttons on the Touch Mouse are stiff, not as forgiving as the Arc Mouse. You can touch anywhere on the Arc Mouse left/right buttons (whether it was towards the front of the button, in the middle, or the back towards your palm, it didn't matter, it would still click with ease). The Touch Mouse didn't respond well to middle clicks (it rarely clicked when trying it towards the back of the button), and you had to be sure to click all the way at the front of the mouse to get it to respond correctly.
The Touch Mouse, although the concept is a nice idea, has a v1.0 affect for the touch scroll wheel, it has some improvement to do. If you barely tap it, like you're not sure if you're going to scroll or just rest your finger there, it will immediately display the Auto Scroll on screen. Also, I do a lot of CTRL+Click, and if my window is not done scrolling if I flicked the Touch scroll, then if I did a CTRL+Click too soon my screen zoom goes into affect (whether it zooms in or out, then I have to go up to the menu to reset the zoom).
Lastly, the folding (or lack thereof) of the new Touch Mouse is not nearly as good as the Arc Mouse. I love how the Arc Mouse collapsed around itself, whereas the Touch Mouse folds flat. Also, the Arc Mouse has a nice pocket to place the receiver in. The Touch Mouse just has a magnet on the back of it to hold it on, and then when it's in the laptop bag it can get lost easily.
I hope this review is helpful to some, I really couldn't find any reviews comparing the 2 different versions of the Arc before I bought it, so I went ahead and bought one and decided to write a comparison between the 2.
I'll stick with the original Arc Mouse, I have since returned this Arc Touch Mouse back to Best Buy.