I can answer your question...Yes! The Harmony wood needles feel like bamboo. Very lovely, too!
Also, this is the magic loop method that I use for knitting in the round with circulars although I knit continental style. The concept is the same, though. http://www.youtube.com/watch?v=BtBSmxGomPk
Then, there's also this method, which requires two circular needles, but there's less pulling and pushing: http://www.youtube.com/watch?v=RybPvCNfrT8
I have been eyeing the harmony interchangeable set, but they don't make the tips in anything smaller than a size 4, so you'd have to by the fixed needles if you wanted something smaller, for socks or something else with fingering or lace-weght yarn...
By the way, how do the wood tips feel, is it kind of like bamboo in that it sort of takes on whatever temp your hands are? I have arthritis in my hands so after buying one addi turbo I haven't bought any more, I try to stick to bamboo in the winter months, but if the harmony sort of warm up too that might be a good option for me.
As for the hat, have you ever tried magic loop knitting? you could use your harmony tip with your longest cable and knit the entire hat on that one needle with no need to change to dpns for the top. Just a thought.
Anyway, impressive needle haul there... very "envy-inducing".