I am not a supporter and I voted no.
I don't think this features is an unfair advantage. It is an advantage but not so big in my opinion.
But I understand why some people feel reticent
I'm in the same position. Not a supporter, and don't really think the autobid would make me feel disadvantaged. I play another game where that is also the position and I don't feel inconvenienced.
Besides, even as a non supporter, supporters having autobid can give us one tiny improvement. If we're in bidding wars with an autobidding supporter, at least the auction won't go on for the best part of another half an hour.