jobel Thanks for the feedback :)
one thing that is weird, when there's a potential head-on-collision the boid doesn't react, it just collides and moves through. Did you do this purposefully?
Don't worry, nobody gets hurt, they're flying over and under one another ;P
Seriously though, there's nothing in the conditions that factors in the angle of the neighbouring boid, only the angle to it, so it shouldn't really make a difference to its behaviour. If you turn up the strength to 1 it looks like they do react a little to boids coming directly at them, just not enough to guarantee missing each other.
It could be that in the 10th of a second that they do the check there's another boid that's closer so they react to that one instead. Another reason could be that the maximum turn rate is too slow for avoiding head-on collisions so although they're reacting, by the time they start turning they've already collided.
Ideally I'd work out a group angle with weighting for proximity but it hurts my head trying to figure it out - maybe for the next version.