The thing that soured me on bpython, after loving it for months, was the realization that I could not scroll back easily to see results of past things (aside from the most recent one). Ipython (and, even better, the qtconsole for it) does that much better.
In a console, I like bpython's interface and autocomplete suggestion interface, but being unable to scroll back and see what I did 3 commands ago was a deal killer.
I had the same feeling about IPython, and I rather liked bpython — and then I discovered DreamPie, which offers a number of features I have found useful in exploratory programming. Yes, it moves me out of both Emacs and my terminal, but it's almost worth it.
Bpython is perfect for me.