Is there a downside to squeezing a real graphics processor into a 3-pound, ultra-thin laptop? Not if it's a MacBook Air.
After extensive use of two versions (the January 2008 original and October 2008 refresh) of the MacBook Air, my conclusion is that a decent graphics chip can--over the long haul--not only deliver the expected boost in performance but, surprisingly, contribute to better battery life while, even more surprisingly, bringing down the heat to acceptable levels.
First, let me address the original Air. I have used this version now for about 18 months. Though it has been remarkably reliable, the Intel graphics (housed in the chipset) is its Achilles' heel. And I'm talking about heat problems, not performance shortcomings.
The culprit for me is video-intensive tasks (I don't play games). Any extended video turns up the heat to lap-warming, or much toastier, levels. This can get downright uncomfortable at times. Not only does the bottom of the laptop get hot but the keyboard too.
Nvidia'a graphics-oriented chipset (the GeForce 9400M) and Intel's updated processor used in the new version of the Air brings the heat down to lower levels. Overall, this Air runs cooler and longer with the higher-performance graphics. (The Nvidia 9400M graphics chipset is also used in Netbooks from Lenovo and Samsung.)
I won't repeat the performance benchmarks, which have been amply cited in many reviews on the Web. Suffice to say, Nvidia's 9400M delivers better gaming benchmarks (see second link above) than the Intel graphics in the original Air.
And what about newer versions of Intel's chipset? By comparison, the ultra-thin Dell Adamo, an Air rival, uses a Mobile Intel GM45 Express chipset (the successor to the Intel GMA X3100 graphics used in the original Air) for its graphics., the Adamo was bested consistently by the Air with Nvidia's chipset.
I also see (which is supported in some reviews) better battery life with the newer MBA. Generally, I can squeeze 1.5 to 2.5 hours (depending on what I'm doing) out of the original MBA. With the newer version, it's 2 to 3 hours.
And now that the Air can be had for $1,499 (versus $1,999 for Dell Adamo), it's a fairly reasonable deal. (Remember: the high end version of the MacBook Air debuted at more than $3,000 back in January of 2008.)