The problem with a tube buffer is that it can only alter the sound. Essentially, its an EQ with 1 setting. It can't add anything. It just covers up problems areas in the music/playback system that some people find pleasing. If you use one and like it, that's fine. That's what really matters. For me, however, I prefer matching my components in such a way that I don't have to resort to using such devices. Its more work, but I think its worth it.
In most systems, some, if not all problems, can usually be traced back to the preamp. Instead of getting a line level device like a tube buffer to "enhance" the sound of the preamp, I say just get a better preamp. Elizabeth's example is interesting. She attributes her VAC preamp to acting as a tube buffer and thereby giving her digital that she can listen to. Looking at it that way does makes sense. To me, though, it looks like she's describing the sound of a good preamp. Either way you look at it, the preamp is definitely the piece that's making it all work. (And maybe the brownies.)
