Overall Score: A
Would I recommend: Yes, with a few minor warnings.
There are plenty of photos online so I'm not including one here. It seems to be very well-constructed, with a good gearing system (hard plastic, but more than sufficient for homeowner use). The gear ratio is impressive, so it produces a lot of pressure for very little walking and doesn't require a pause/repressurize walk--it works continuously at the same rate.
The S15 includes a strainer cap and a wide enough opening that adding liquid is easy. I had a bit of overspill from my bucket addition, but very little.
The wheels handle well even in slightly uneven terrain, although very uneven ground would be an issue (as it would be for anything with wheels).
Changing heights is a snap. It's a simple knurled knob, but once you set your preferred height I don't see that you'll adjust it much. Take the height measurements with a grain of salt.
Changing nozzles is also a snap, simply align and twist in the cap.
The machine is built for 5'8" to 6' people optimally, shorter ones will find the machine tilts a bit toward them, giving a slightly uneven spray. Moving the machine closer to you will solve that issue for shorter people. Taller people will wish to move it away from them or accept a shorter spray.
It arrives fully assembled with only the handle folded. Unfolding and setting up the handle took me about fifteen seconds.
It weighs around 20-25 pounds, give or take, when empty, so it's extremely easy to move. I have no issues lifting it one-handed and carrying it.
The S15 includes three spray nozzles, coarse, medium, and fine.
The spray is amazingly even with any given nozzle, and feathered at the edges. I tested each at two walking speeds and reported the results below.
Although it advertises itself as a five gallon sprayer, it holds six gallons (or quite close). The final formal mark is at 5 1/2 gallons, with about a half gallon margin to the top of the sprayer.
I found the machine to be kind of heavy at completely full. 25 pounds base weight + 5 gallons of liquid is approximately 70 pounds, or half my body weight. In my case, I'd fill it to three gallons. People with reasonable body weights shouldn't have an issue, but this stands as a warning for smaller-built people.
Spray distribution is incredibly even, as I mentioned above. With the feathered spray, I'd use a tracker with any herbicides or pre-emergents, although that would be my general recommendation with most sprayers.
I tested the spray at two speeds, a slower walk (perhaps 1.5 MPH) and moving fairly quickly (2.5 MPH). The manual recommends a swifter walk than many people would do normally, so if you have leg or back issues that may be a problem.
I measured the spray width with a simple tape measure, and at the highest setting on the distance dial (setting #1, 5'). These measurements are full spray width, so divide by two for the distance on either side.
Coarse Nozzle: 2' spray with 1' feather on each side
Medium Nozzle: 3.5' spray with 1' feather
Fine Nozzle: 2' spray with 1' feather
I have no explanation for why the fine nozzle sprays a shorter distance than the medium nozzle. At the time I tested it was completely wind still.
Coarse Nozzle: 3.5' spray with 1' feather
Medium Nozzle: 6' spray with 1' feather
Fine Nozzle: 3' spray with 1' feather
Needless to say I'll be using the medium nozzle and adjusting my solution density accordingly. It's possible that my medium nozzle is cut slightly differently, but I definitely verified that it was the medium nozzle!
I only tested the coarse nozzle on the lawn with a solution of iron, and the output was approximately what the manual says it should be, give or take some. The next time I'll use the medium nozzle and if it differs I'll mention that.