While I like full-size mice like the Logitech Performance MX, the Arc Touch is great, if you only need a mouse in addition to the other input methods.
Now, given the ergonomics I wouldn't want to use it 24/7, but the flat design is great and not much of a bother to carry along.
The only thing I'd prefer is a regular scrolling wheel, since the scrolling touch mechanism does have its quirks. Oh, and it wouldn't hurt if those buttons would click just a tad bit earlier towards the top.
Little probs aside, I highly recommend it for mobile situations.