A presentation of Treetop by its creator, Nathan Sobo, finally won me over. Plus, Treetop is a Ruby gem, thus easy to be installed. Or thats what one would expect it to be. Not so on Debian.
Read it here
Debians position on Ruby gems is, essentially, to not support it because it has its own package management system. Instead, Debian insists to package selected Ruby gems as Debian packages as that would be the only way to ensure the familiar software quality Debian is known for.