The Logitech t400 Zone Touch Mouse is a conventional two-button computer mouse, with a touch-based scroll 'pad' instead of a scroll wheel. See also: Logitech t620 Touch Mouse & t400 Zone Touch Mouse review: made for Windows 8.
The pad allows for both vertical and horizontal scrolling, and is suitably accurate. However, it offers no tactile feedback. It would really have benefited from a 'clicky' mechanism as used by Microsoft on the Arc Touch, where a small speaker beneath the scroll pad generates a quiet but detectable 'click' as you scroll, very similar to the resistance you'd feel when scrolling with a real wheel. (See also: Logitech t620 Touch Mouse review.)
Like a normal scroll wheel, the pad functions as a third mouse button when pressed. Because of its shape, though, it's much easier to press without accidentally scrolling up or down a bit. Anyone that uses their middle-button (gamers without a hardcore gaming mouse, I'm looking at you) will find this helpful.
Half of the scroll pad also serves as a dedicated Windows 8 'start' button, which works identically to the Windows key on most keyboards. It also works in Windows XP, Vista and 7, but is rather pointless in those operating systems. It's conveniently positioned, but doesn't get in the way -- in a month of use, I don't think I opened the start menu by accident even once.
The sides of the mouse are coated in a ridged, rubberised material that provides excellent grip and control. It also helps avoid a sweaty mouse-hand on hot days, as the ridges allow for air circulation.
The t400 connects to your PC via Logitech's 'Unifying receiver', which takes up a single USB 2.0 port and can connect to up to six peripherals. This is good if you've also got a compatible Logitech keyboard, as it saves you a valuable USB port.
Overall, this is the best 'normal' (not designed for gaming) mouse I've used in a long time. With the addition of tactile feedback to the scroll pad, it would be a five-star platinum product. As it stands, still highly recommended.