Almost nil. What does it sound like, can I play it (nope... i.e. is it too heavy, does it balance, etc.). Occasionally, is it seriously cool (I have a Westone Rail :)
That's pretty much it.
I really, realy dislike Frank Zappa.
And I went off Foo Fighters very quickly. Some decent tunes, but a wash of hi-hat in absolutely bloody everything... He's supposed to be a good drummer??!
It's the price that gets me. A mutilated bass with pretty much everything anyone might consider to be "original" removed, and they want five grand for it?!