Last night was my first encounter with Soar. I too was thoroughly confused about how it worked. I don't believe I'll be playing with soaring creatures blocking movement.... that just makes no sense. I will however demand that no figures stop movement beneath a soaring creature. That would just get too complicated.
I'm not sure I understand how the LoS works for a soaring creature. Can the creature see 'over' trees? Or is the creature supposed to play by the same rules as if he was on the ground?