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I should warn you that this review is essentially a comparison between the Zenbook and the MacBook Air. Being a MacBook owner (albeit one who is not loyal to the Mac operating system, despite liking it a lot) my first instinct was to make that comparison, and I was rather surprised to find that the Zenbook did pretty well.
The main advantages of the MacBook Air are its light weight, strong build quality, long battery life, and easy to use operating system. So how does the Zenbook size up on these counts?
Firstly, I should note that while being light-weight, the Zenbook definitely heavier than the MacBook Air. This is because some compromises have been made to give users far more disk space compared to the Air. It has two disks - one big 'normal' hard drive, so you have plenty of space for all your stuff, together with a small fast solid-state drive (SSD) which Windows uses to speed things up (e.g. the machine comes out of hibernation very quickly).
Build quality is very good and feels solid. However, when looking closely at the casing, and things like the placing of the rubber lining around the screen, it is clear that the attention to detail and factory quality control isn't comparable to Apple's. The keyboard is excellent and feels good, and is also backlit (you can adjust the brightness of the lighting). The trackpad is also superb and has some of the same gestures you may be used to on the Mac.
Battery life is great and comparable to the MacBook Air. There is a 'performance mode' - where it wakes up immediately from sleep - that uses more power, and a 'battery-saving mode' - where it saves state to the SSD. In battery-saving mode the time taken to 'wake up' was hardly noticeable, so you can keep it in this mode all the time.
Windows 8 and the 'Metro' interface is a pleasure to use. Everything 'just works' and it's very easy to get things done. The Social app that integrates your Facebook, Twitter, LinkedIn etc into one feed works very well and is very quick to set up. The Mail app seems less featured than the Mail app on Mac, but does most things you need to do. Things like voice search work well. The Windows Store works superbly, apps install with one step and is again a pleasure to use. The Update process has been refined so it largely operates in-the-background and much less intrusively than on previous Windows versions, and doesn't require immediate restarts.
The most annoying niggle is the one with the trackpad's special gestures, the most important of which is the two-fingered one used for scrolling - every now and then, after waking up from standby, the trackpad does not respond to any gestures (but basic movements & clicking works). I don't know if this is a driver problem but it shouldn't matter - in 2013 and with Windows 8, this is a basic feature and not an extra, and it should be completely reliable. I couldn't figure out a way of getting gestures back except by restarting Windows. I have never had such a problem on the Mac.
There are some smaller niggles too which Asus could've easily avoided - Asus has McAfee anti-virus software installed as standard, which prompts you to buy a subscription after a 1-month trial. This is completely unnecessary as Windows 8 has its own perfectly good anti-virus built-in. I had to manually uninstall McAfee. The Asus software update seems to happen independently of the Windows Updates, which prompted an intrusive request to restart the machine. But thankfully this happened just once. Also there is supposed to be (according to the included documentation) a wired Ethernet adapter included in the box, which wasn't there. Most people won't need this anyway, and Apple doesn't include one with the MacBook Air (if you're going to buy a super-portable machine like this, you're unlikely to want to hard-wire it into a box for internet). But it still shows a slight lack of attention to detail by Asus to say something's there when it isn't.
All-in-all, this is a great machine with a great operating system, and at the current price point decent value for money.
(This review has already been posted on Amazon, under my account M. Marikar)