Sony's Vaio X Series is one of the new breed of laptops that pushes the definition of ultra-thin to new limits. Although not the absolute thinnest available, this new Vaio is also compact and lightweight, making it a desirable, if pricey, mobile client for the executive traveller.

Available to buy now, the Vaio X Series has a footprint smaller than an A4 sheet of paper and an 11.1in screen, characteristics that mark it out as an ultra-portable, a segment of the laptop market that emphasises portability, but often at a premium price.

This new Vaio certainly has a premium price. Even the entry-level model costs £1,299 but, at just 13.9mm, it is thinner than virtually any other laptop we are aware of except for Dell's recently launched Adamo XPS. The Vaio is also one of the lightest with a start weight of just 655g (depending on choice of battery).

For this price, you get a specification that is not much better than a typical netbook, which makes the Vaio X Series a stylish but costly option for those needing a highly portable system to carry with them when travelling.

However, we have concerns about whether the X Series is sturdy enough to survive everyday use on the road. The system's screen bends alarmingly and even the chassis can be deformed noticeably by exerting only modest pressure.

In tests, we found the Vaio very pleasant to use, although somewhat underpowered for anything but basic productivity tasks, while its compact size and light weight mean you hardly notice you are carrying it. We were also surprised at how long the battery lasted, considering the slimline format.

The specs
Our review unit was the VPC-X11Z1E/X model, which is based on a 2GHz Intel Atom Z550 processor with 2GB of memory and a 256GB Flash SSD instead of a hard drive, to help keep the weight down.

This model ships with a standard battery that leads to an all-in weight of 780g, which still makes it one of the lightest laptops we have ever tested. A smaller and lighter battery pack can be specified with the 'configure to order' version of the X Series, which is known by the model name VPC-X11X5E.

Despite its low weight, the X Series still provides a decent range of connectivity options, consisting of 802.11b/g/Draft n Wi-Fi, Bluetooth and a built-in Everywair HSDPA modem for wireless broadband, enabling buyers to stay connected virtually anywhere.

It also has two USB ports, VGA output, Ethernet connector, headphone jack socket and two slots along its front edge for SD Card and Sony's own Memory Stick Pro Duo Flash storage cards.

As a measure of just how thin the Vaio X series is, a hinged cover forms one half of the Ethernet connector, because the laptop's chassis is too thin to accommodate a standard size Ethernet jack.

We liked the Vaio's 11.1in X-black LCD display which features an LED backlight and looks nice and bright in most light conditions with a native resolution of 1,366 x 768. Also appealing is the keyboard, which has its keys spaced apart in what the Americans call a 'chiclet' design that makes typing very easy and pleasant for such a small system.