Testing large tablets like the ViewSonic ViewPad 10Pro reveals that currently in the tablet market, you have to go thin and light. Toshiba's recent announcement of a much thinner Android tablet proves the theory. The ViewPad is just unwieldy for anything but casual use, mostly at a desk.

That's actually one selling point, though. The brick-like lack of mobility at least means the tablet will stay flat on a desk and won't slip around.

ViewSonic offers a small dock you can use for propping up the tablet, and you can also connect a USB hub and then a mouse and keyboard. When you use the HDMI-out port to connect the tablet to a desktop display, the ViewPad 10Pro becomes a desktop PC.

Of course, slate PCs with this functionality have been around for years. However, it's handy to run Android 2.2 in a full-screen view with a keyboard and mouse. The only other way we've done that recently is with a Motorola Atrix smartphone. But the desktop operating system, once the tablet's docked, isn't actually Android anyway.

The tablets-as-desktops approach has some advantages, but not as many as we'd hoped. For one thing, few Android apps ran correctly. We'd imagined playing Angry Birds at a desk, then switching over quickly to Word and typing up a long document, then going back to Android.

Until ViewSonic figures out the app support problem, its ViewPad 10Pro even has limited appeal in a desktop configuration.