What is the earliest company to use this method?

Not sure.

What are the advantages or disadvantages of this type of neck joint?

The main advantage is that a neck reset involves loosening some bolts, inserting a shim, and tightening the bolts again, rather than a prolonged battle with steaming and prying and poking and praying to get the neck off without breaking anything - so it usually costs a fraction as much to have done.

I'm not sure there is any disadvantage except that "It can't be right because that isn't the way Martin used to do it!" You can get into arguments about whether there's any difference in tone from the neck joint construction, on any of several forums, but I don't know of any agreement one way or the other having been reached.

What guitar makers use bolt on necks?

Well, I know Collings does. That should be sufficient proof that the quality of the instrument in not affected by the use of the bolt-on neck, in and of itself.

Peter.