Thanks you very much. We should fix the behavior in 3.3 for sure. I'm
thinking that we may be able to backport the behavior fix to 2.7 and
3.2 as well, since it just makes the behavior generally "better" (and
for most folks it won't matter anyway).

I'm not sure where the somewhat odd rules for .islower() come from, I
think in part from the desire to have "".islower() be False but "a
b".islower() to be True. Intuitively, this means that .islower() means
both "there is at least one lower case character" and "there are no
upper case characters", but not "all characters are lowercase". I
forget what we do w.r.t. titlecase, but the intuitive meaning should
not change. Although personally I don't have much of an intuition for
what titlecase means (and why it's important), perhaps because I'm not
familiar with any language where there is a third case for some
letters.