I think Larrabee is something for AMD and NV to worry about in the long-term as a platform. Larrabee as a product however, I think gives less cause for concern. A first-gen radically new architecture that is unlikely to surpass the performance of its contemporaries is unlikely to gain significant market share. If Larrabee is to succeed, it will probably be in the console space where devs can truly take advantage of all that programmability. A couple years later it should catch on in the AIB market once enough people have experienced what Larrabee can do in a console environment (both devs and consumers).