I read Mr Schomer's 'bible' front to back several times, and it spite of getting nice crema, and following the rules as best I could my coffee was still bitter most of the time. One day, by mistake I ground some coffee very fine and over packed it slightly. The result was a very very slow pour, dripping out, a bit oily but absolutely DELICIOUS. It was also pretty short and not much crema. It was the best taste I ever got out of my machine -- and it seems to be easily repeatable.
Am I missing something here? It seems to me the only way I've found to make delicious espresso.
Comments appreciated

Many people enjoy the flavor of a very restricted (ristretto) shot.

It seems to work better with some coffees and worse with others.

If you find that it tastes good, how could it be wrong?

For the most part, I tend to pull my shots ristretto, in one way or the other... Meaning maybe only a bit slower, or maybe a long droopy shot. 45seconds is usually the longest I will let a shot go, and Im usually under that a bit.

I can only think of TWO coffees that I enjoyed pulled as actual Normale Doubles, 2oz in 25-27seconds. The Honduran Finca La Tina from Intelly, and the Guat La Maravilla from Ecco.

I do not know exactly what you mean by "very, very slow" pour. For my part, I very rarely drink shots that pour shorter than 30-35 seconds but also rarely like the taste of a pour that is much longer than 45 seconds.

I find that as, Jeff wrote before me, it is a matter of what coffee (and the condition of that coffee) you are using. And most of all, as Jason and Chris implied, the only rule that should apply is your taste.

there is no such thing as heresy is what we're saying.
personally, i've never had a shot that took more than 30s or so that was well extracted to my taste.
and then you have people posting above that they basically never like shots that extract in less than 30s.
obviously, part of this is related to the coffee being used - but it's mostly personal taste.

enjoy.

No -- I'm talking about 90 seconds or more. VERY slow. I would like to get more volume and better crema. But I guess you can't have everything!

I've gone as long as sixty seconds when dialing in a new coffee, just to see how long it takes to get to 1.5 ounces. Using that as a scale, it's a bit easier to make a jump to 'close' rather than sneak up on it by degrees. I also have a habit of taking a taste of sink shots so that I can get an easily identifiable taste of 'bad technique' so that I have an idea of what to change if I taste a teensy bit of it in future shots.
I had one go almost a full minute, (like 55 sec) and it was on it's way to the sink when I took a bitty sip. I was halfway to tipping it out when I realized that it was good, and juggled to keep it in the cup.
I've since discovered that you can get reasonably reliable chocolate sweetness, but at the cost of complexity in the cup. Depending on the coffee that you have, you may be giving up a lot of subtle facets and flavours, but if you like them better than the best you can do with a 25-30 second pull, more power to ya! ; >
Like everyone says, drink what you like. Schomer has published what he likes, but if everyone always liked the same things, there'd always be a line.

I'd like to add(for some reason), that one of my "Coffee new yrs Resolutions", is to learn how to pull a proper double shot, that tastes good. Meaning, 16-18grams, 2.0-2.5oz, under 30seconds. This was inspired after reading some sort of old articles on Coffeegeek, by Mark, about Ristretti and Normale pours, which is harder/easier, which is "more rewarding", how competitors pull shots in competition.. etc, etc. . .

Its something I want to explore, simply for the purpose of becoming a better [home]barista. Ive been trying/playing with it, and Im learning that such shots may not be AS coffee dependent as I originally thought. That is subject to change, many times, as I continue to try new things. One thing stays constant. . . Its not easy for me.

(My other coffee new years res. was to pull good shots, using a Kenyan Single Origin. And THAT one has been completed. . . Thank you George Howell, your current Kenyan 'Spro is quite delicious!)

In the morning coffee thread I posted how I was drinking stale coffee and how I made it taste good, discovered accidentally. This what you described sounds a bit similar to my experience, specially if you had high temp on your machine, and that may be very much the case since you wrote usuallly your espresso is bitter.
My question is if you use fresh coffee?
Then if yes, just skip all the Schomer's mystic pizza stuff and watch the machine temp to be not too high, grind the coffee (finer then for the schomerish stuff) , use something sharp like a needle to level it, then tamp.