I wouldn't be surprised. Mindflayers aren't OGL, are they?
Even still, I kinda like the Athasi. Mindflayers are nasty because of that "alieness" of what they are. The Athasi make for a more identifiable kind of scary.
Like finding out the community of humans you're staying with really want to eat your brains.
I dig this book. It's got a lot of useful stuff in it.
Damn, never thought Derro could be that nasty... did you take a look at that fungus-huul'ach thing in the back? <shiver> that's a cross between alien-scary, and Athasi scary.
And hey, he just wants to eat your brains!