I do have a netbook, and it has the slightly faster Atom N280 at 1.66Ghz with a 667Mhz FSB (most are N270's at 1.6Ghz/533Mhz) and the RAM maxed at 2GB. The only poker I use it for is occasionally single tabling without a HUD, or railing other people's games (like the CC League games). If I seriously want to play on the go, I bring my laptop. The netbook just isn't a pleasant experience.
Even the dual-core Atom's are woefully underpowered compared to conventional CPUs, and would only improve performance slightly over the previous generation netbooks. Netbooks simply aren't intended for heavy processing -- by definition they are intended for low-duty use like browsing and note taking, maybe movie watching with the newer N450 CPUs (mine sometimes hiccups and lags during video playback). And screen resolution, though improved slightly on some of the latest models, is still severely lacking. All of these compromises are necessary to achieve the portable, battery-sipping goals for the device, but all are counter to a good multi-tabling poker experience.
Even when stacking to overcome the resolution problem, running multiple tables or even just HEM/PT3 and a HUD, is going to seriously degrade performance to the point of being unplayable.
I agree with Hamm -- if you're looking for a portable poker playing machine, buy the beefiest laptop you can find. And my preference is the most resolution possible, which is why all of my laptops have 1920x1200 WUXGA+ resolution. I have a pixel obsession, lol.