I owned a high-end E61 group machine for many years and like many similar owners I thought I was doing OK. Sometimes I had difficulties getting a truly sweet espresso, but going ristretto often solved that to some degree. Then not too long ago someone presented me with a deal on a Londinium L1 I could not refuse.

Initially I wasn't overly impressed with the L1. It seemed larger than it really needed to be, it had a noisy vibe pump, a single boiler, plain wands, and was devoid of a PID. But the espresso... rich dark chocolate with no tannic aftertaste. Yes, I had to use a looser grind since the brew pressure is lower, and the water temperature could be all over the shop depending on how long I waited for the thing to warm up, or if I decided to flush it. But no matter what I did it was hard to get anything but delicious espresso. Over weeks of use of this machine the reality slowly dawned on me...

The engineering effort and expense that goes put into maintaining stable pressure and temperature over the length of an extraction of espresso is based on a fallacy. The extra engineering and expense that goes into providing temperature/pressure/flow profiles from pump machines is ridiculous. A lever machine is the best, the simplest, and the most cost efficient way to get great espresso. I'm just sorry it took me so long to understand this.

Discuss.

I don't disagree. But this is a hobbyist driven thing. You can make great shots with the Microcasa or Cremina, but both require a long learning curve and very finicky temperature management. Home sized single group commercial machines, that had more intuitive and simpler operating characteristics, were hard to find until recently, when the Strega and Londinium models led to a solid line up of semi-commercial machines. Now, an eqaully solid line up of profiling machines are a growing alternative.

We are not going to see levers and profiling machines in cafes until they move straight shot making to the brew bar, since they are too slow for the latte line. If there is not enough consumer demand for this; there will be an increasing split between the way pros and amateurs make shots.

for OCD, lots of variables = excitement to measure and control obsessively and play God in a cup

For ADD, Lots of variables = welcome distractions from the torture of staying focused and mastering boring fundamentals

For zen, lots of variables = the delicious complexity of the world reflected in the microscosm of a cup of coffee

For pragmatists, lots of variables = a set of controls available to solve a problem should it occur

I love my Flair... it converts pressure and timing into an intuitive physical movement guided by my over educated and under used brain. But I suspect every set of equipment and the compensations we adopt with it relate to our success with particular roasts and flavour preferences.

On the other hands, maybe I should try Black Cat again. When I was using my Gaggia, I got a great shot just at the bottom of the bag and never bothered again. Could be an interesting challenge on the Flair, esp tweaking temps with my PID kettle

I used to own a La Pavoni and considered a Londinium, but for a similar price I went for a more compact, less finicky, temperature stable, better steaming, more silent machine with unparalleled profiling flexibility: the Bianca

^^^I suspect that is a matter of personal opinion and ultimate desire. This was the point of the OP's question.

I wouldn't be surprised to hear of enthusiasts going the way around, and wondering why the entire world does not go on E61.
As Jim wisely says, is a hobby driven thing.

For myself, I find falling in third David's definition, the Zen one

the delicious complexity of the world reflected in the microcosm of a cup of coffee

.

The Export is relatively a poor performer compared to high end equipment. But I found that you need to apply yourself a lot to get a bad shot.

My temperature management is all to touch the group right behind where the vent hole is:
too cold: wait
ok: pull
too hot: stick a wet rag, wait a minute and go.

And then I leave the variables to wander thru unexpected results: I never get a bad shot and they all taste slightly different, I've called it "rainbow effect" as it allows you to taste all the hues of your coffee.

To make an example, I've stopped to grind finer as my beans age from the beginning to the end of the bag. This attempt to chase a consistent taste thru the bag ultimately led to a lot of frustration.
Now I just increase the dose and the tamp as the coffee tends to stream more easily, Is more fun and allows to feel much more nuances I'd miss otherwise. And to be honest I never suspected to find such nuances in a cup, before trying a lever.

I can see why levers are not the norm in commercial environments, I'm mainly talking about home use. I also appreciate that not every kitchen can accommodate a lever without some inconvenience.

I'd add to my original post that the spring lever seems a natural way to extract espresso. It starts with the highest pressure and temperature at the beginning of the shot and reduces over the extraction. As the coffee has less goodness to give the extraction becomes gentler which means a reduction in tannin and other nasties. For a Bosco group at least, the max extraction pressure is 6 bar which necessitates a coarser grind which again leads to a smoother result. It really makes me wonder why most machines focus on 9 bar sustained pressure throughout the extraction. I suspect that that approach is effective for light roasts, which I assume are not the most common. I certainly prefer a medium roast.

Also, I see mentions of the '"bottom of the bag" syndrome. I makes me wonder if it's literal because it's not a problem I have. I generally buy coffee in 5lb batches (cheaper than multiple 12oz bags), let it age for a week, then pack in ZipLock bags and freeze. Then as I need beans I transfer them to an 8oz glass jar (keeping the remainder of the bag in the freezer) and store in the fridge. If there is a degradation in the quality of espresso over time I don't notice it.