The Vesper Bar is basically the lobby bar for the Cosmopolitan. It has a cool vibe and is very well located for people watching / making comments as the endless parade of people walk by. As one would expect at the Cosmo, it is aimed at the hipsters and those thinking themselves "in the know". Even so, the service is good and they make solid drinks. This is the best bar in the Cosmo if you are looking for a "mixology" experience.
We really like the menu. It is set up in two columns. On the left are classics made in the traditional recipe with quality ingredients. On the right side is the Vesper twist on the classic that is of a similar flavor profile, but with greater complexity or a thought provoking ingredient swap. For instance, one can order a classic Manhattan or the twist: "The Mulberry". The variation was in every way better than a Manhattan -- deeper, more complex, and a long finish. We tried several of their variations on a classic and thought they did an excellent job.