The ACE socket libraries are solid. If you are trying to port a standard implementation of sockets you can't go wrong. The ACE code sticks to a rigid development paradigm. The higher level contructs are a little confusing to use. The rigid paradigm causes some anomolies with exception handling. There are or used to be situations where string value pairs being passed into an exception with one of the pair being null causes an exception throw in the exception that will boggle you. The depth of the class layering is tedious when debugging. I have never tried the other libraries so can't make an intelligent comment.
