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.

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.