The Logitech T650 is a large (129mm square) wireless touchpad specifically designed specifically to make using the gesture controls in Windows 8 feasible for either a desktop or laptop PC.
It has a large glass surface with just a little friction and feels very much like the glass-topped touchpad in my HP laptop, albeit much larger. There's a gentle slope to the unit making it easy to rest your wrist on the desk and reach to the front or back with little stretching. Build quality is great, with a substantial, solid feeling.
The excellent: Hardware & single screen gesturing
First impressions on initially unpacking the device are excellent - with the packaging being a pleasure to open with minimal wastage.
A micro USB cable is included for charging the battery, along with the tiny 2.4GHz proprietary unifying receiver (which works for up to 6 Logitech devices). Given the pain I've experienced trying to get Windows Bluetooth drivers to work on a plethora of devices I can forgive Logitech for going proprietary here - as the installation process was seamless (Win8). I simply plugged in the receiver, turned the touch pad on, and basic mouse functions worked. A sticker on the underside of the unit led me to the Logitech website to download the full SetPoint drivers for further customization.
In use most of gestures work really well. 2 fingers up and down scrolls web pages vertically very smoothly. For horizontal motions you have to remember that 2 fingers is scroll, and 3 fingers is forward and back - both of which work well across both desktop and metro style applications. 2 fingers also drive the zoom - in a motion that I think will become second nature - and just as easy as using the Ctrl-scroll wheel function in Windows 7.
3 fingers up takes you instantly to the Win8 start screen (or if you're on the start screen already it switches back to the desktop), and down drops you back to the desktop view - both of which I can see myself using on a regular basis (although there's something to be said for hitting the Windows key to go to the start screen, and then to start typing the name of an application). 3 fingers down while on the Desktop with applications open minimizes open applications, so that you can see the desktop below.
On a single screen system the swipe from left gives you a graphical view of the last-used Win8 style app, and lets you switch to it smoothly. As is true of Win8 itself - the whole desktop appears as one of these, and it doesn't let you switch between all apps (for which you have to continue to use AltTab).
Clicking is accomplished either through a light tap on the surface, or a harder press to activate the button built into the rubber feet. Whilst it looks like there are two independent buttons on either corner I'm fairly sure that it is only one button. The touch surface determines if you're clicking in the left corner or the right one.
Given you're occasionally going to need to use the click function - the T650 isn't really optimized for use on the armchair for a multimedia PC, or other soft surfaces (like your leg).
I haven't quite got my head around how the 4-finger gestures work, so might leave them for another day... (although the 4-fingers up to maximize a desktop app is a good one).
If you're used to using a pen & touch Wacom device for photo editing - then you'll find that the touch on this is much better, but you'll still need the Wacom pen-based interface for photo editing. From a quick test the drivers didn't conflict - and I was able to use both together on the same system.
Cracks begin to appear: Click and drag
Click and drag has always been harder on touchpads than with mice, and Logitech have obviously thought long and hard about how to optimize this action (and have listened to user feedback, and released an update in mid Nov). There are two ways to left-click and drag.
The first is to use your thumb to click the button, then while holding the button down, to use your finger to select the object and move it, releasing it with your thumb. After a little practice I think this will become second nature - and I think is the way Logitech intended it to work.
In one of the more recent releases of the driver they've also enabled a second double click drag mode. In this case - you double tab the object, and on the second tap hold your finger down - then you can move the object. This is how most laptop touchpads work today - so will be familiar to most.
When it comes to right-click & drag, things get a touch more complicated. As Logitech choose to only implement a single click button on the body of the device (rather than 2) - to get the right click you have to touch the zone in the bottom right hand corner of the device, AND push down enough to activate the click (which is fine for my thumb, but a little tougher on my little finger). The zone starts roughly 5mm from the edge and extends around 30mm square - so to hit it with your little finger, you have to make sure you're not right on the edge of the touchpad.
Once activated (with a click in the touch zone using your little finger), then tap the object you want to move with another finger, move it, and then release the little finger.
It does work, but I keep finding myself below the zone and issuing a left click/drag rather than right click drag. Hopefully I'll get it with a little more practice, or Logitech will think of a better solution at some point.
I did try configuring right click to be 'Click or tap with 2 fingers' which is fine for simple right-click, but you can't then drag the object.
Further cracks: Multiple monitor mode
Windows 8 was obviously designed around a single screen touchscreen interface, and in that mode the touchpad works very well. It is easily an upgrade on the small touchpad built into most existing PCs, and I can see myself using it in place of a desktop mouse.
When it comes to multiple monitor extended desktop mode (hit Win-P, then select Extended), Microsoft haven't quite optimized the experience as well as in Win8-native only mode - and when you add the touchpad, it just gets a little more confusing.
Charms can be brought up on both screens by hovering in the bottom-right corner, and from there you can open the Start screen. Once you've opened this on a particular screen, then all of the gestures that interact with Win8 apps operate on that screen. i.e. the 3-finger up swipe doesn't bring up the start screen on the one you're working on - it bring it up on the screen that last had the Start screen active.
The right-swipe to bring in the charms, and left swipe to task-switch work the same way - in that they interact with the screen last used for metro apps.
This feels a little unnatural - as I'd have expected this to work on the 'currently active' screen - i.e. the one holding the pointer.
Alternatively it would be nice to be able to designate one screen as the Win8 Start screen so that you could designate the smaller laptop screen to be the 'Win8-native home screen' while dedicating the larger external monitor to be the desktop screen.
Hopefully this is something Logitech and Microsoft will address in a future update.
So does the T650 make Win8 usable on a desktop?
If you're used to using a touchpad on a laptop, and are migrating to Windows 8 on a single-screen non-touch PC, then I'd say unreservedly yes. The benefits you get from gestures under Win8 outweigh the complexity of right-click drag on the desktop.
If you're using a multiple-monitor setup, it does work, but you just won't gain quite as much primarily because Microsoft hasn't quite optimized the interaction between the Win8 mode, and desktop mode across both screens. That said, it is quite usable - and I'm going to continue using mine on my home PC.