The 1.4GHz Core2 Solo processor is quite a bit faster than your average Atom, and its HDMI I/O port and draft n Wi-Fi are a welcome addition to such a tiny machine.
OK, now for the bad stuff.
As for the remainder of the machine, it doesn't feel much better. The only way to describe the plastic body is "cheap." Not only does the glossy black finish reveal a strange, flecked iridescence under light, tap on the palm wrests with your knuckle and something about the hollowness of the pitch assures you that it could easily crack under a moderate amount of pressure.
When you hold the Air, it's an incredible sensation not just because of its size but because of how sturdy it feels at its size. The X340 misses the pleasure of this dichotomy and gives us what I'm willing to wager is the most fragile laptop I've ever put my hands on.
Performance
Believe it or not, while the X340 is burdened by Vista's heavy footprint, it's quite usable. General navigation seems infinitely faster than running Vista on a true netbook, like the Dell Mini 12. The benchmarks support the fairly fluid experience of the OS.
The X340's graphics chip is the Intel GMA X4500MDH. All you really need to know is that this architecture is nowhere near as good as NVIDIA's 9 series stuff, like the 9400M. And it's not powerful enough for heavy gaming (the 9400M is already scraping the barrel pretty hard). You can see the two platforms side by side here:
In reality, the X340 performs up to most of my expectations (since I never believed it could handle 1080P clips anyway). Just don't expect it to be some sort of dream multimedia machine. In that regard, the X340 is like a netbook on steroids—fine for general use, just not juiced up enough to handle the next tier of graphics-intensive operations.
The battery lasted 1 hour, 43 minutes - ouch*
You could probably stretch the life beyond two hours with a few tweaks, like gimping the processor or squiting at the screen, but if you're planning on watching a movie during your next flight, it'd better be from the 90-minute Pauly Shore Archives.
*MPEG 4 playback, Wi-Fi on, screen at full brightness, "balanced" performance. You can purchase an 8-cell battery that should hit 3 hours for a bit more weight
The Sad Conclusion
I should be thrilled with the X340. It's lighter than many netbooks that have smaller screens. While not as tailored as the MacBook Air, hey, it's damn close. It also runs Vista at a reasonable speed.
But if you're looking purely for the lightest way to fit a 13-inch screen into your bag that's waaayyyy cheaper than the Air, and you only want to use a computer for 1 hour and 34 minutes at a time, then I'm not stopping you.
[Additional research from Geekbench]