What a journey of discovery it's been:
1) Things are becoming known about it's standard failure modes at least through the five-year point.
1a)The 3-way solenoids tend to go buzzy after about 3 years, are VERY easy to replace and not hard to find. They go in and out of stock at ereplacementparts.com. Popular item. It still works fine buzzing, but it eventually got annoying to me so I replaced mine.
1b) The o-rings on top of the stainless steel steam boiler seem to be good for 3-years max. They are also easy to replace, standard size and shape items. $10 delivered by Amazon Prime will give you two human lifetimes worth.
1c) In the "big pimpin' " category... Because it uses standard Ulka vibe pumps, it is ridiculously easy to replace with one with a the threaded brass outlet, that you can screw a proper brass OPV on. This is "big pimpin' " because the stock OPV is not a common failure mode at least up to the five year point. Except for a few folks who constantly adjust, (something that may well be superfluous, see section 2), putting extra wear on the plastic OPV. Me? I set mine to 9 bar with a blind filter called it good.
2) Useful ability to keep up with the current trends in extraction experimentation
2a) Low pressure extraction: Breville has a patented means of controlling the Ulka vibe pump output. Only it's limited to pre-infusion. But by fortuitous unintended consequence, they have given us full control of pre-infusion both output power and duration. You can set pre-infusion time to 99 seconds, so it never "leaves" pre-infusion, and then you can set pump output electronically, to from anywhere between 60% and 90%. So I can do low pressure extractions from anywhere between 1 1/2 BAR to max... All through keystrokes on the panel. And it nails it.
2b) Pressure profiling. Easy 10 minute "mod" with a Phillips screwdriver. Totally reversible for warranty work. No cutting fabricating or actual modifying (that's why I put "mod" in quotes). All you do is remove the microswitch from the hot water knob inside the cabinet, and let it dangle or zip tie it out of the way. To profile during a shot, you open the hot water knob and it bleeds pressure away from the boiler in a FULLY linear and unbelievably easy and responsive fashion. And you can vary it back and forth (why you would want to, I don't know, but you can). It's the most direct and responsive manual profiling I've ever seen. On any machine.
A surprising LOT of good here.^^^
From this thread, check this quote from a pro barista here in Socal:
Quick look at Breville Dual Boiler Espresso Machine
If you can believe it.
A friend/my boss sold his GS/3 to get the BDB.
And he is super happy. I went over and checked it out. Now I have one also. These machines are no joke. Totally worth it at twice the price.
I love this machine.
And even though, (Regulatorjohnson/Jon Stovall excepted), it's been largely ignored by the kind of experts who could _really_ do something with it, I've just GOT to wonder what kind of magic could be gotten out of it, if some of our techy experts were interested. Full digital control of temperature and pressure by: Reverse engineering the source code, or simply replacing it with an Arduino. The possibilities are miles ahead of where we are today, if the "right" people were to take an interest.
In the mean time, like Jon, I'm tickled pink... still... even five years on. Fortunate that I can afford whatever I want, my plan to get a proper saturated brew group machine nevertheless remains on hold, until this machine either limits me, or can't be repaired for a pittance. Neither of the latter is even beginning to loom.