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The original Asus Zenbook UX21 really helped to make the case for Ultrabooks, showing that if you want a speedy, thin, light laptop you don't have to buy an Apple MacBook Air.
The Asus Zenbook Prime UX31A is a natural successor, with a faster processor and graphics, and additional USB 3.0 port, more storage space and that vastly upgraded screen.
The result is that, unsurprisingly, the Asus Zenbook Prime comes with a premium price. And it very nearly meets it with a premium product, but falls short in one very important area - the battery.
We liked
The Asus Zenbook Prime UX31A's screen, of course, is the big showpiece. It's not just the resolution, but the overall quality. Great colours, excellent viewing angles, good contrast ratio - at 13.3 inches, it's a 1080p masterpiece.
Performance really is just as speedy as you'd hope, with Windows 7 picking up almost instantly from standby, and even booting barely giving you a wait.
Really importantly, it's also comfortable and pleasant to use. The trackpad is good, the keyboard is great, and it's made really well.
We disliked
There's one major and obvious letdown with the Zenbook Prime: the battery life. Though in practice, with very light use, you'll get more out of it than we did in our benchmarks, it's still badly behind the competition - even the much, much cheaper competition.
The speakers are disappointing, too, and it's a shame that Asus includes so much irritating bloatware on its machines.
The price is an issue, as well, especially in light of the battery life. The Asus Zenbook Prime UX31A isn't inherently overpriced at £1,500/$1,500 when you compare it to other high-end Ultrabooks, but you have to ask whether you're happy spending that much money for this kind of machine.
For many people, it'll be secondary to larger, more powerful computer - you'd have to ask, do you really need to spend this much? And if you do, will the battery life be good enough for you?
Final verdict
The Asus Zenbook Prime UX31A is a premium computer with a price tag to match. The build quality is excellent, the performance is great for an Ultrabook and the screen is top-notch.
Sadly, the battery life makes you think twice about its good points when you're spending that amount of money - we're just not sure that it's worth it for all that many people.
If you want a high-end Ultrabook, we recommend the Asus Zenbook Prime UX31A as long as battery life isn't your main concern. If you just want an Ultrabook, we suggest starting a bit lower, with its little brother, the Asus Zenbook UX32A.
