We compared the performance of TCP-NIO against TCP in a four machine cluster.

TCP-NIO Number of messages read per second:
   13402
   13155
   13344
   13107

TCP Number of messages read per second:
   13490
   13462
   13476
   13440

CPU utilization was around 64%.

Read the details at http://www.jgroups.org/javagroupsnew/docs/Perftest.html