This is a great idea: make a simple system to apply water at pressure through a coffee puck. No other frills, really!
The machine is well-made, constructed of well-machined aluminium parts, heat-proof plastic and a silicon O-ring and combination dispersion screen/gasket. (Yes, you read that right. Strange, but it works). The porta-filter is very nicely made and easily competes with other, more expensive models.
I have read interested non-owner's concerns that all that aluminium would act as a heat-sink and reduce the water's temperature well before it gets to the coffee. In fact, the water is only in contact with the heat-proof (and, it seems, utterly non-porous) plastic. There is virtually NO heat-sink effect. I'm not enough of a geek to go and measure the water temp before and after, but suffice it to say that if I pre-heat the porta-filter and cup properly (a necessity for any machine) I get lovely non-sour, non-bitter espresso.
The design of the piston is such that a silicon O-ring moves a bit as you raise and lower the piston. When you raise it, the O-ring moves to uncover small holes which allow the water to reach the coffee. When you lower it, the O-ring covers the holes and allows pressure to be applied. And to allow this design, the face of the piston is concave. This allows air to be let into the cylinder along with the water. And as we know, air compresses easier than water. The result is that the cushion of air absorbs some of the pressure that you apply by lowering the levers and prevents full pressure from reaching the water going through the coffee. But as I just read in an earlier review, one possible solution is to simply add as much water as possible (thereby reducing the 'air cushion') and only take the coffee that you want. Sounds like a good idea! But I'm not convinced that O-ring seals as well as it should too. [Edit: tried the extra water trick this morning - works brilliantly! O-ring seals just fine.]
The 'group head' and porta-filter are a little high above the base, certainly for espresso cups, but it is easy to put a spare little container on the bottom to raise a cup. And I do like being able to press directly into a larger cup for the morning lattes. (By the way, I use a ebay'd Benjamin and Medwin for milk frothing - does a really fine job!)
I'm delighted to be heating my water by non-electric means and I find the whole system works extremely well. That being said, I should point out, though it would be obvious to most of you, that this is really a machine for someone who is willing to adjust (and interested in controlling) all of the variables in the making of espresso. This is similar to a La Pavoni (which I used to own): care in beans, roast, grind, tamp, temperature, pressure, pre-heating all contribute to the quality of your brew. But once you get the knack - no complaints whatsoever. This is truly espresso, as opposed to moka-pot coffee (which I like too!).
A few more points: the construction and fit of the parts is excellent. If need be, everything can be easily taken apart with Allen keys for cleaning, repair, replacements or hot-rodding. I emailed the company with some of my suggestions and praise and they responded (!) enthusiastically and sympathetically. And once again, I must stress that being able to heat water by whatever means (preferably relatively eco-friendly) is really revolutionary. It's a little like the invention of the hand-cranked portable radio. Well, not even slightly, but you get a sense of my enthusiasm.