It's my experience, if you pull your own espresso shots, that the grinder is important in order to deliver the right fineness without heating the beans. However, grain size, volume of ground coffee are related to the oiliness. Plus you need to tamp the puck properly, ideally 30 lbs of pressure - which is why I got an Espro tension tamper that delivers a consistent tamp. I find that after hitting the button on my semi-automatic Salvatore Espresso machine, there should be at least 7-8 seconds before any liquid comes out and for a double shot, it should take more than 20 seconds from start, ideally 24-28. Thus you get a properly extracted shot and good crema. Since I also prefer lattes, I steam the milk and have pretty much figured out, by holding the pitcher (or nowadays I steam milk in my big coffee mug) how hot is just right. Over 160F and the milk tastes burnt - which is what happens at least half the time when I get a drink at a coffee house. There are people who are a magnitude more paranoid/detailed oriented than me - coffeephiles are just like audiophiles. They get into factional measurements of water temp, flushing the unit first if it is a heat exchanger, etc. The king of the hill for a home unit is the La Marzocco GS3 at 6500; La Cimbili is also good. As for grinders, I have a Mazzer Mini doserless and it's awesome - the only one better, but uglier, is the Versa Dynamics (of Versalab turntable fame).
If I had to use a super automatic, like a Jura Capresso, I'd get the Nuovo Simonelli Microbar as it provides heavy duty boilers, grinder etc.