in the end it's just a preamp pedal lah. all the preamp does is eq and maybe gain. i think the tone is determined by much more than a preamp. unless you do massive eq on your preamp, perhaps it could make your tone more and more artificial.
you must remember that a preamp pedal is in series with the preamp of the actual amp itself. if you screw around too much it could get messy and complicated. even when the amp is set to flat, it will still colour the tone. even if you bypass the preamp and go directly to the power amp for that matter, there will still be colouration. not that anyone will do that though, because it is very unlikely that a preamp pedal can give you the same functionality. if you DI, then you don't really have a choice.
in a live situation all this doesn't really count for much, because there is too much noise live for it to matter. or rather, a 2 or 3 band eq is not gonna make much of a difference. but the psychos who buy expensive preamps have special needs, such as recording etc. in those kind of contexts, subtle differences mean alot. jbarker has a huge fire hydrant cum tube DI which i'm sure gives him a priceless edge. boutique preamps aren't completely placebo effect, because nobody out there can fool all the people all the time.
where all gear is concerned, as you start to push the limit, subtle improvements will cost alot of money.
for me, i don't even own a preamp. used to though. i found it as useful as having a completely transparent buffer in my chain.
but if i had the money WHY NOT MAN? :twisted: