In one word: no. For all intents and purposes, things are fully backward
compatible (except if you were depending on some bugs which have now been
fixed :-).
As far as upgrading to v3.10 goes..., actually, procmail v3.11pre4 has less
problems (read no known bugs, contrary to v3.10). The only reason why
it hasn't been cast into a real release yet is lack of time (and because the
SmartList part of things needs to be tested).
Wouldn't it be better to decouple the version numbers and
release schedules for procmail and SmartList. Just put a big
note in the README for SmartList that says what version of
procmail it requires. I would think that staggering the releases
would be less work and allow more frequent updates.
Richard Coleman
coleman(_at_)math(_dot_)gatech(_dot_)edu