I use Favourable Beginnings and maybe Luck of the Far Realms on the two tadpole-curious idiots because I feel they would try them and both skills feel the least intrusive. The rest just doesn't interest me. It changes nothing in the story and I like my class skills better than the tadpole ones. I guess the final battle is supposed to show you how cool the mindflayer abilities are, should you have resisted them before, but it only convinced me that I really don't care for them at all but that I absolutely need Sorcery Points in my game. Thank you Mizora!