This question is best answered by Nik, but they appear to be the same as all the other JJ tubes I have purchased over the years. I have purchased a couple dozen at least over the past 3-4 years. I usually get mine from Bob at Eurotubes and they have consistently good performance. Just like any tube they are not necessarily the best for all applications, but they are for most applications.

As far as shipping across the world, since they are manufactured in the Czech Republic I would imagine just about everybody but Czechs get them after shipping "all over the world" and this can be said for almost any tube. 

I went through this same thought process and in the end, Nik's prices are so good I just went ahead and purchased from him. The JJ ECC83S is a hot pre-amp tube and should be used when you want early break-up or more distortion.