Sony took the wraps off its Vaio UX50 ultracompact PC at a news conference in Tokyo today and we got five minutes to play with this cool-looking device.

It's about the size of a paperback book, so it fits in a jacket pocket, but it runs the full Windows XP OS and is based on an Intel Centrino processor.

Dominating the front of the PC is the 4.5in LCD (liquid crystal display). This has a touchscreen so, like the previous Vaio U model, you can operate it as a tablet PC and slide up the display to reveal a full qwerty keyboard underneath. The keyboard is backlit, which will be handy if you're using the machine in low light, but we found it a little difficult to use.

The keys are almost flush with the case and don't move much when pushed, so we never really got a good feel for them. They're also small - the entire keyboard is only about 12cm wide - so we constantly worried that our fingers were hitting neighbouring keys, although in the brief time we used the computer we didn't get any misspellings.

The position of the "enter" key at the far right of the keyboard made it difficult to press. This was compounded by its slightly curved shape to match the case.

The screen is sharp and bright. It has 1,024x600 pixels resolution so full-screen web browsing is possible, but would be difficult for the poor of sight. Everything in the Windows menus and input boxes was readable - nothing was so small that it became a mush - but we did find ourselves squinting at some things.

There are a couple of handily located zoom buttons on the righthand side of the case. These helped, although the need to include zoom buttons shows how small everything on the screen is.

That may not be a huge problem because the UX50 seems to be more about fun, on-the-go computing than manipulating Excel files or writing novels. For many users the portability of the device will more than compensate for the small keys and small letters.

Because we had only a few minutes with the UX50 we weren't able to test other features, although some of the more notable include a fingerprint sensor, built-in camera (just above the main display so you can video conference) and Bluetooth wireless. Sony is selling a companion Bluetooth GPS (global positioning system) receiver that feeds global positioning data to the PC.

It's difficult to hold the UX50 in your hands and not be impressed about the amount of technology crammed into it. It compares favourably with Samsung's Q1 ultramobile PC, which is based on the recently-launched Origami platform, and will definitely draw looks when you use it in public.

At today's launch Sony said there's a second version on the way. This will use flash memory in place of a hard-disk drive so it's likely to be a little lighter and more expensive. That should launch in the middle of this year.

The UX50 will go on sale in Japan on 27 May and in the US in July. In Japan it will cost around ¥170,000 (about £820) and in the US will cost about $1,800 (£950), Sony said.

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