Ooh, shiny! Petzl's Grigri is ubiquitous (look it up, rock apes, it's a real word) at gyms and crags everywhere and for good reason: it locks auto-reliably. Note that there was a recall on Grigri 2's with serial numbers where the first five digits are between 10326 and 11136. Go to http://petzl.force.com/GRIGRI2RecallWebForm but don't let it stop you from getting an awesome product.
At 5.9oz the Grigri 2 is two ounces lighter than the original. It's also about an inch shorter on the long axis and half an inch shorter on the short axis, although overall it feels much more compact than that. The big selling point is that version 2.0 handles ropes 8.9mm to 11mm, whereas the original was only 10mm to 11mm.
If you liked the original Grigri you'll love the new version. Aside from being lighter and smaller and handling thinner ropes, the Grigri 2 just works smoother, like buttah. For a truly seamless belay experience pair it with Petzl's Freino carabiner, harder to find but worth it with a little horn that allows full control for lowering a heavier partner. The good folks at Petzl deserve credit for taking a great product and making it signficantly better, and extra credit for clear instructions that include detailed drawings of usage in various scenarios.