Uh... Did I miss the part where he explained what was wrong with existing clients? Without a clear, specific problem to solve, this is going to be an exercise in wasted time.
I was looking over the mailing list and just about everything I see mentioned can be done with Mutt (or Sup). Personally, I use gnus on emacs. Add in some org-mode magic and you have just about everything anyone could ask for (well, search is not as nice as I'd like it).