From: Werner F. Bruhin [mailto:werner.bruhin@free.fr]
I use Boa for some time now, a bit over a year, and I am very
happy with it.I like its integration of tools, GUI editor, source editor,
debugger etc.[...]
Recently looked at SPE, but frankly didn't give it enough time to be
able to fairly compare it with Boa (one thing I missed, or at least
couldn't find was a debugger - which to me is an absolute must!).
I have used Boa a lot, but only because it's the best there is, not because
it's good. The SPE interface is *much* cleaner. Problem with SPE is that it
incorporates too much "Blender" stuff, while Boa too much Zope stuff.
However, Boa does integrate editor with GUI layer-outer with debugger, it's
the only free tool that I know of that does that. Until I have time to build
my own of course 
A combination of the best of Boa and SPE, based on
plug-ins so the interface contains *only* what *you* need. Cheers,
Oliver