All and all, I found the dual boiler with great temp stability, mechanical preinfusion and a 2 year warranty at less than $2k to be the sweet spot for me.
Positive Product Points
Dual Boiler, frothing power, great temp control, 15amp or 20amp selective use, mechanical pre-infusion option.
Negative Product Points
Upgradeable sides (as in the physical sides of the box that make up this machine) would be a plus (not that the current ones are a minus). I would like a stainless frame and a stainless drip tray at this price point (the E-61s are all stainless at this price and below), and an external timer (this should be part of the standard control). Had minor problems with defective water sensor and pump set at 9.75 bars (these were all minor adjustments).
The double box came very well package by Chris Coffee. They had tested the machine and Scaced it before shipping. I could tell this was done and that water was run thru the system. Chris coffee did this in short order and then repackaged it very nicely. My Mini included a hand written note mentioning a +4C offset according to the technician. I called to understand his protocol. Or to put this another way- is his offset the same as mine since our process may differ? He mentioned that he warmed the machine fully, performed a 2oz flush, waited 30s then another 2oz flush, wait 30s then test (pull). Close enough for me. In sum, the box was well packed, nicely delivered and machine tested.
The setup was easy. Remember to fill the boiler at start-up using the start-up procedure. I was impressed with the dual boiler and the temperature control. Varying the brew temp by 1-2C changes the taste! I was impressed at this change and the repeatability of the extraction process. This is the best part about this machine- repeatability without effort and great espresso. The pour over and 15amp convenience is nice. Any issues about noise and the aesthetics are over blown IMHO. I use the volumetric dosing most of the time. My machine came with the preinfusion option. For milk drinks, the steam is powerful and I get a lot of use from the water dispenser for preheating cups and Americanos.
For my wish list, I would like the sides to be upgradeable. Something like the La Mazocco GS3 (with a nice logo) or stainless or carbon fiber sides would a plus. A stainless frame and drip trap would be nice at this price point. I choose not to buy or use the $200 optional time. I do turn the steam boiler off when not in use and have heard that the machine cost about $0.10 per day to leave running 24/7 without steam boiler or about $0.25 with steam and brew boilers running (according to the helpful S1 owners on the S1 owners forum). An insulated steam boiler would be part of my wishlist, but is not enough of a wish for me to diy upgrade or to pay more for the feature.
All and all, I found the dual boiler and temp stability with preinfusion and a 2 year warranty at less than $2k to be the sweet spot for me.