The options for quill stems these days is pretty limited so with the use of a threadless adapter the number of stem options really increases.
I like the fork on my '99 Trek and it has a beautiful NOS DX headset so I used a 1/8 adapter and an Easton stem that matched the position I had with the old adjustable stem.
With the adapter I also have the option to adjust my bar height which is something you cannot do as easily with a thread less set up.
They are a great bit of hardware to have when you have to deal with 1/8 threaded parts which are not at all common.