The only opinion you need to have is that the default network stack is not good enough if you want to respond fast enough to play with the big boys. If you're ok with ms-level latencies, don't bother. There's a degree of customization you should do beyond just swapping out the default stack or putting in a different kernel to get what you want.
Wow, Small World. Just flipping through the openfabrics 2009 workshop attendees, and stumble on two very familiar names. david cohen (now with GS), and scott ross (ubs). dave and i used to be counter parts (we were both head of tech arch and strategy, for two separate divisions at same ibank, boy quite a few years ago now).