First off I wanted to say, again, great job!
Next, I had a recommendation (not just for this tool but any that allows placement (random) of objects:
Would it be possible to introduce a variable that randomly changes the direction of the object. For instance, if I use a particular type of tree they are all facing exactly the same way (0 degrees). With a "randomizer" they would automatically be facing different directions, thus adding to the realism. I am not sure if this is possible, but it would help.
Last, I wanted to that I went back and redrew some road segments and it seems that the shorter the distances involved (still using several points), the straighter the roads. It is the long roads that begin to swerve dramatically.
This tool has helped save me countless hours. In my last map, I spent weeks just placing roads in what your tool takes maybe 45 minutes (from nothing to final touches). Fantastic!