Who has a TeeBird and does not use it? Do you never need to throw straight?
I carry both a Teebird and an Eagle X. The Eagle X is actually straighter for me, but I can get a little more distance with the Teebird. The Eagle X is used much more.
As for the original post, I rarely use my understable midrange that I carry. Yesterday it was a star Stingray. I won't take it from my bag because, when I need it, there is no other disc that will do.