A lot of money for a good tool
Your ears really are the best tuning tools. I still tune by ear 90% of the time. However, in loud environments or with drums that are particularly messy sounding, this thing is a life saver. I use mine largely for tuning concert basses, timpani, and the occasional temperamental marching bass. It's probably about as good as my ears; don't worry about the mechanical problems that come with things like Torque keys and the like.
My only complaints are the lack of an upward facing dial and an easier to use rim gauge... the little piece of metal isn't awful, but it's clumsy to work with sometimes. I would check out Tama's newer version of this product, but I already spent money on this one.