Emacs is one of my favourite tools on a computer. I love Lisp (even Elisp, which is getting closer to Common Lisp as time goes on) and I love the interaction, but Emacs is not good for serious terminal/shell work and it, sadly, is pretty annoying as a tiling "window" manager.
Maybe with multi-threading it will get better, but until then, I can't see a compelling reason to work exclusively in Eshell.