I am also a huge fan of TD's!
I think that it's the only genre that could make me so hypnotized by the process, that I would sit in my chair for 8 hours. That's also why I purposefully tried to softly limit the length of a single session in Plantlike to a few hours - didn't want to make a game that actively hurts someone's health :D
And while I also appreciate some "classic tower defense" games where enemies have a certain strict path, I guess I always preferred TD's that are more "spatially open" and have more roots in the strategy games - like Creeper world, Rise to ruins, They are billions etc.