Microsoft's got a new mouse, the Microsoft Arc Touch Mouse. Here's a video of its designer Young Kim introducing it:
Now, let's philosophize about it the Xah Way. First of all, it's a portal mouse. That means, it's not the most comfortable, ergonomic, mouse. It's not for professional heavy-duty 8-hours-per-day use.
Being a portable mouse, its attraction is limited, because, if you are on the go, you may not need a mouse at all. For example:
So, now for the few who really like to have a mouse for the go, i suppose this is fine. Not sure the space-saving matters that much. As far as ergonomic goes, Apple's mouse is worse.
I do not recommend Arc Touch. Instead, i recommend “Microsoft Touch Mouse” or “Microsoft Sculpt Touch Mouse”. See: Microsoft Touch Mouse.