Instead of using an Intel Atom N570 processor with really poor integrated graphics, the new Samsung Chromebook 550 uses an Intel Celeron 867 processor with much better graphics. From an Atom CPU to a Sandy Bridge CULV processor, there's an important step up. Intel Celeron 867 is a low-end processor that lacks many features that are available in Core i3/i5/i7, but it's 3 times as fast as the old CPU (according to Google).
The new Chromebook doesn't meet Intel's requirements to be called an ultrabook, but it's almost there. It has an Intel Core CULV CPU, the height is 20 mm instead of 18 mm and the battery life is more than 5 hours (it's actually 6 hours).
The old Chromebook was pretty expensive for a netbook, but the new one is cheap for an almost-ultrabook that actually has a matte screen, a great keyboard, a powerful touchpad, it boots almost instantly and is not hindered by an operating system that gets in the way. Now that Chrome OS has a more familiar interface and Chrome can run native apps, the new Chrome devices could gain more traction.