It's certainly more elegant, although I'm skeptical of the purported performance gains as well, simply because so many optimizations have been thrown into traditional kernels.
If you are using a more minimal hypervisor (see my other comment on the parent), then there do seem to be some measurable gains. I've seen a few papers in this style:
We describe the hardware and software changes needed to take advantage of this new abstraction, and we illustrate its power by showing improvements of 2-5 in latency and 9 in throughput for a popular persistent NoSQL store relative to a well-tuned Linux implementation.
That said, a simple application like memcached might be currently latency-bound by the kernel's network stack, but a more complex application that reads from disk (even SSD) won't be.
