Ultraportable notebooks always fire PC Authority’s collective imagination. No sooner is one out of its box than it’s passed round the office, as we contemplate ditching our desktops and attending meetings and business trips with nothing more than a sliver of technology to keep us company.

Everything about the Asus U1 is calculated to weigh next to nothing and consume the least amount of power. The CPU is one of Intel’s lowest-power units, the Core Duo U2400. There’s nothing stellar about the 1.06GHz chip in terms of raw performance – our review sample was still running the RC1 of Vista and so didn’t benchmark fully, but it will be some way behind larger notebooks. It certainly doesn’t preclude normal office jobs, though, and the real selling point of the U2400, apart from the fact it’s dual core, is its TDP (Thermal Design Power) – a meagre 9W. So even though the U1 is around half as quick as our Intel Pentium D 840 benchmark PC, its processor generates about a fifteenth of the heat.

Internal components are restrained, but there’s nothing overly disappointing inside. The 1.8in, 80GB hard disk might prove a slight constraint for those who wish to take a well-sized video library with them, but the standard gamut of work applications, files and images shouldn’t see you reaching for a screwdriver for a few years. Graphics power isn’t capable of gaming, but the Intel GMA 950 adapter is capable of running Windows Vista Aero with ease.

Professionals will appreciate the inclusion of a TPM module and fingerprint reader. The almost implausibly small proportions of the U1 mean there’s no built-in optical drive. This caused divisions in the PC Authority office – for some it’s a must-have, while others claim to have happily gone without an optical drive in their notebook for years. An external optical drive is included, and the dual-layer DVD writer is tidily implemented, drawing its power from the notebook itself.

The screen is a bright, 11.1in panel with a native resolution of 1366 x 768. The glossy finish isn’t particularly suited for professionals; we had problems with background reflections while working in the office. But the upside is, under the right conditions, terrific image quality. The U1 flew through our technical tests, providing an excellent set of results. RGB colour ramps faded to black too quickly, but we were perfectly happy reviewing high-quality digital images. Viewing angles are also good enough for a few people to crowd around. The small, 0.3-megapixel webcam built into the bezel is a nice touch too.

Build quality is generally good. The keyboard in particular is excellent, and, in spite of the keys themselves being a little small, we managed to get back up to speed in no time. There are a few areas where the construction materials feel a little lacking; the monitor lid and wristrest are key examples. On a desk this isn’t a problem, but we found ourselves hesitating before stuffing the U1 into a bag and running to a meeting.

But it’s otherwise impossible to complain about the U1’s ultraportable credentials. Even with the larger, six-cell battery it weighs only 1.2kg, and runs for 6hrs 47mins under light use and 2hrs 42mins under intensive use. Switch the batteries over and the weight of the U1 drops to just 1.1kg, running for three hours under light use. Running our intensive benchmarks away from the mains reduced this to just 1hr 20mins, though. But, combine the two batteries and, with a break in between to switch them over, you’re looking at nearly ten hours under light use. Even considering the notebook, power supply, both batteries and the external DVD drive, the U1 collectively weighs just 2.2kg.

There’s plenty of competition for your money in the ultraportable market – just look at last month’s UMPCs (May 2007, page 40); tiny, fully fledged Windows systems complete with touchscreens and keyboards. But neither has a high-enough resolution LCD to make Windows a practical proposition, and using Windows primarily via a finger and a touchscreen can be frustrating. The U1 is cheaper than either of the UMPCs and far easier to use.

It can’t quite work its way to the top of the A-List, though: the Dell Latitude D420 is faster and has a larger screen. The Dell is heavier but, at 1.5kg, is still a fairly negligible addition to a shoulder bag. It’s also $700 cheaper, besides coming with Dell’s solid three-year on-site warranty. The Asus does come very close to tripping up the Sony VAIO VGN-G118GNB (May 2007, page 36), though. The Asus is smaller, lighter and cheaper, but the VAIO beats it on the grounds that it has a built-in optical drive and a stunning nine-hour single-battery life. If you need an ultraportable for work, the Dell D420 is the place to stop looking. If you simply want to save every last gram, there’s plenty to recommend the U1.