This is a laptop that divides opinion almost like no other. Some accuse it of being a glorified, overpriced netbook. Others simply pick it up and swoon.
No-one can argue with the VAIO's design credentials. At 12.2mm, it's precisely as thick as an iPhone, and its matte-black finish is reminiscent of a sheet of graphite (the only design oddity is its brown bottom). Even the wafer-thin screen drew admiring gasps.
The main chassis is similarly slight. There isn't room for a conventional network port, but Sony has cleverly created a hinged port: when you want to use it, you raise two tiny feet and this gives the hinge room to expand enough to slot in your cable.
But what's controversial about this laptop, and the reason so many people fall instantly out of love with it, is the processor. It's a 1.86GHz Intel Atom Z540; it supports Hyper-Threading, but the fact remains: it's an Atom.
To see if it was fast enough, we used the X-Series as a workaday machine for office tasks for a week. It had to power two monitors and cope with Word, Excel, Outlook, Firefox and multiple utilities - all using Windows 7 Professional, not XP.
First impressions weren't great. With Aero's fripperies switched on, the X-Series felt sluggish and annoying. Once we optimised Windows for best performance, though, things improved markedly.
Without Aero's overhead, menus snapped to attention, there was no lag and it became perfectly usable. It just looked a little like Windows 98. We were also happy once inside a program. Despite using testing formulae in Excel, for example, the X-Series didn't feel slow.
It's a shame the graphics chipset is Intel's GMA 500 chip, which was designed for power frugality rather than speed. But this does reap dividends. The X-Series kept going for more than seven hours when idle, and even when pushed to its limit it survived for three hours.
Considering this laptop weighs a miserly 766g (1.05kg with the power supply), that's some achievement. And if you're after true stamina, note Sony will be selling an extended battery. This straps onto the bottom of the X-Series, and Sony estimates it will last a phenomenal 20 hours.
There are niggles, and the first is the cramped keyboard. The isolated keys give greater margin for error when typing, but the tiny right-Shift, full stop and cursor keys are all awkward to hit. It also seems odd to include such a tiny touchpad when there's plentiful space below the keyboard.
The display again split opinion. It has a notable red bias, which affects skintones, and its horizontal and vertical viewing angles are a little limited. You could also argue that its 1366 x 768 resolution is too high for an 11.1in screen, although if you're finding it a struggle to read system text you can enlarge it easily via Windows 7.
The X-Series includes pretty much every wireless connection you could ask for. There's Bluetooth, 802.11bgn WLAN, plus an integrated 3G modem that supports up to 7.2Mbits/sec.
Sony backs all this up with a two-year collect-and-return warranty, and we were impressed by the build quality of this little machine as well. The screen flexes as you'd expect, but when we gave it a solid bash on the lid there was little sign of it on the screen.
Despite all this, it's tricky to see who's going to buy the X-Series. Will a senior executive really be willing to put up with the occasional waits and niggles? While we understand why Sony opted for an Atom - there's no room for the cooling system needed for even an ultra-low voltage Core 2 processor - it will put off too many people.
So is it just a laptop for your travels? Well, the X-Series is eminently usable on the move and we still can't get over just how light it is. Slip it in a briefcase and you simply won't notice the extra weight; it can even slide into your case's side pocket, it's that slim. But you only need to look elsewhere in Sony's range to see more practical options.
The TT-Series and Z-Series offer far greater power in packages that are bigger, but to an acceptable degree.
The real problem for the X-Series is its price. It includes a solid state disk, inevitably adding to the cost, and Sony must recoup some of its substantial R&D outlay. Who, though, can lavish $1899 on a vanity laptop such as this? Very few.
This exclusivity may well end up adding to the X-Series' allure, and if you buy one expect admiring glances from all who see it. Just don't tell them there's an Atom inside.