Looking back through mail, I noticed the above thread that was still hanging with respect to 1.0.
A few minutes ago, in 8494, I went ahead and committed a change that makes show block in tkagg and fltkagg, just as it does in all the other interactive backends. As usual, other developers are *welcome* *to* *revert* this change; but I think it is an important one to get into 1.0 if possible, since it helps smooth out an inconsistency that keeps surprising users.
Again, I hope someone can test 8494 right now. It would be especially useful if someone with an older OS version could test it. I run ubuntu 10.04, so there is always the danger that something that works fine for me might not work for someone with an old RHEL or Windows XP or OSX 10.4. The change affects *only* show() on tkagg and fltkagg. I don't expect it will magically make all backends work exactly the same in all possible environments (ipython -pylab, idle, etc.), but as far as I can tell it is a step in the right direction; I don't expect it to make anything substantially worse.
In retrospect, I think I was too cautious; I should have simply made the change in svn 3 weeks ago. The only way to get much testing of something like this is to put it in by default--not as an option requiring deliberate testing--and see if anyone trips over it.