I've been called "it" many times since the start of my transition. Personally, I'm not bothered by it, but I'm not a particularly sensitive person. During this awkward in-between stage, I fully expect people to be confused about what to call me. Usually, they're just providing me with honest feedback as to how I'm being perceived. It's obvious if someone is just being an arsehole, and their input holds no validity in my mind, anyway.
Having said that, I can still understand how many trans people may be offended.