i've been thinking a lot about the difficulties surrounding espresso.
in particular, about the inter-related complexities around creating and roasting espresso blends and signature style and taste and barista equipment, skill and technique.

let me explain...
here at Stumptown we use Mistral machines in the coffee bars. the Mistrals are fantastic machines - but they have some unique traits. these unique traits (to be fair) are in fact the reason why people choose the machines -- they're obvious improvements over the other options. in particular, their combination of La Marzocco style double boiler setup with pre-infusion results in a very different (and superior) extraction profile from what you'll get with most other machines. we run these machines at specified brew temp and brew pressure. finally, we are in Portland - which gives us high humidity and moderate temeratures most of the time.
our espresso blend (Hairbender) is forumlated to a specific flavour profile and style. it is a complicated, dense and rich espresso with nice dark chocolate notes, good fruit and a heavy mouthfeel.
the Hairbender is evaluated by traditional cupping and by production at our bars.
the other day i was chatting with a friend (a skilled barista) who was struggling to get the flavour profile he was looking for out of the Hairbender. he asked me about the brew temp, target extraction time, etc that we use. i realized that, given the equipment he was using, our settings were not going to result in a duplication of our flavour profile.
i suddenly realized that, when i was at Spellbinder, our machine setup, extraction time and volume and even dosing volume for the Hairbender was entirely different from what we're using here at Stumptown... but the end results were shockingly similar. and i remembered that it had taken me a lot of tweaking to get those results. i ended up running a brew temp that was almost 3 degrees higher than what we run here, a pressure that was about 3/4BAR lower, dosing about 2 full grams less for a double and pulling shots that were a little less volume in about 1 additional second.

all of these leaves me intrigued -- but also frustrated.
when our coffees are evaluated, even if the baristas are incredibly skilled, the results are nearly entirely unpredictable. about the only solution i can think of is to get our hands on every reasonably possible espresso machine out there and experiment to get target parameters for each one (not only machine settings but all the way down to dose, extraction time and volume, tamp, etc.).
and even then there would be no guarantees. there is a coffee expert who i really respect whose tastes in espresso run to what i would consider to be oily, over-extracted and incredibly acrid. his extraction times are regularly between 35 and 40 seconds for a double.

there is a feedback loop here.
the selection of equipment feeds the evaluation of results which affects the formulation and roast of espresso which is based on the signature style and taste which is dependent upon the equipment...
you get the idea.

oh... there is a happy ending to this tale of concern... because i'd worked with the Hairbender on La Marzocco machines, i was able to provide feedback for parameters and because the barista in question is skilled he was able to provide input about flavours. in the end things work out.