It's rock solid (ever since the late 2010 update). I had a late 2008 MacBook Air and had to have the hinge tightened after a year. I don't think that will be necessary with the 2011. The hinge design is completely different.
It's fine unless you add the weight of a hard cover to it. At least that is what I found for myself. With my perforated hard cover, it is a little flimsy.