OTAs are awesome!! They are my favorite part I never used in any real project. (In part because if you want something like a voltage controlled filter then there is always a special chip for that that is cheaper and performs better than the comparable OTA circuit.)
I once heard the story (don't know if it's true) that Robert Moog always wanted to use OTAs in a product, but never found an application where it was justifiable because there was always a cheaper (and equally good) way to do it without OTAs.