Yes it does help and you should not discount a PR0 if it is from a good web master because as they raise the PR of the directory, that helps you also. You have to remember all domains started at one point with PR0.
Yes it helps...if not to increase PR but to improve your sites ranking. It all depends on the directory. You may want to have a look at the sites already listed in the directory before submitting. A good directory adheres to a set of guidelines and actually rejects sites. Matt Cutts once mentioned something called "Value-Add" when it comes to directories. There are good directories and there are directories that are nothing other than link farms(...) Good directories will never allow you to manipulate anchor texts or stuff site description with keywords. Good directories actually care for the search industry and sufers in general...
yes, i agree with a lot of the people. submitting to quality directories can help raise PR, keyword ranks, and creditability. i noticed that competitors do the same thing as well. about 30% of their backlinks come directories.