I used pound as a load balancer and currently stumbled upon this article about load balancing with
pound. The writer used pound for the site Justin.tv. Pound used about 20% cpu and in spikes up to 80% which is quite a lot. They now switched to nginx and the load dropped to about 3% cpu usage. After reading that i tried it on my server and the performance of nginx is quite good. I did not have such high loads that i got a great advantage now, but it feels a bit faster.
If you need to balance websockets you can take a look at this post, they are using the nginx module tcp_proxy to balance websockets. I had problems getting this running with pound although there is a success post around. I will definitily give it a try.