I wrote this in a private message but I decided to share. The reason most people move to levers is flavor but over the years I prefer levers for mostly the lesser known reasons. So I wanted to highlight them to help anyone who is new or looking to get into a Lever. Please add your experiences.

1) Cleanliness. Since the piston pushes out all the water there isn't an abundance of pump driven water and water pressure to dump out of a 3 way solenoid. So dissolved coffee doesn't get sucked up into the group and out the solenoid into the tray when you end the shot. So yes that means no more backflushing as the piston stays mostly clean. A brief flush will clear most whatever remains on the shower screen/piston face. Also since there is no turbulence from pump driven water pressure so the top of the puck isn't disturbed much by water flowing in (which leads to the sides of the portafilter being messy on a pump machine).

2) Forgiveness. The delivery of pressure doesn't require absolute perfection in technique to maintain the integrity of the puck. So it is easier to get a great shot even if you don't perfectly distribute, tamp, etc. My wife pulls great shots on spring lever machines while she struggled with our commercial HX machine (she would forget to flush too and burn the shot on an HX).

3) Almost silent. The only noise from a direct plumb spring lever machine is the light clack of the Pstat (or none with pid) and the slight click of the autofill solenoid.

4) Simplicity of design and less parts to go wrong. No pump, no motor, no gicar, complex electronics board, no 3 way solenoid with coffee flushing through it.

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And as for flavor...I'll throw my quick summary on that too if you are new to spring levers:

The flavor is mostly due to the tapering pressure profile = more flavor and thicker mouthfeel

Lowering lever begins a soft preinfusion (low pressure water fills up over the puck forming into a column of water) then releasing the lever the spring takes over pushing the piston down on the column of water delivering full pressure. Then as the spring unloads (the lever slowly lifts) the pressure tapers off until the end of the shot. So as the shot is extracted the tapering pressure matches the increasing flow of the puck to reduce channeling and extract more flavor out of the coffee.

Jason

3 and 4 most definitely! Quiet is my favorite thing about levers. I love the silent Cremina or Pavoni and a hand grinder.

I think 4 , simplicity adds to the art of the entire experience. Its a quiet orchestra in the morning leaving me with a fantastic latte to start the day.

I definitely need to dress up my post a bit more with more colorful adjectives and analogies. It definitely is a quiet orchestra in the morning!

Low maintenance and the ability to focus on the taste of the espresso, rather than how we got there. My Leva is quiet, reliable, cheap to maintain, and makes stellar espresso.

I would like to add one:

5) Historical value. As I understand, this is how espresso as we know it really got started, and despite the relative simplicity still not surpassed by complexer techniques (although that is subjective, but it's not like how flatscreens made the old tube tv's redundant).

Levers are more restoration friendly. They are simple by design, so modifications and work arounds are easily fathomed.
Levers are beginner friendly, they beg to be tried, and most often, they yield successful shots.

As for the noise factor - here's a nice long shot, with a door interruption at the end.
http://www.youtube.com/watch?v=TNIJSXy4Fsw

It's a quiet moment in a hectic life.

Yes! the perfect response to Koyaanisqatsi

I agree with everything above. My machine is a manual lever, and I enjoy the smaller size, simplicity of use and maintenance, and the ability to manually control the shots, not necessarily in that order.

I really need to acquire a Cremina. I really enjoy watching the assembly videos of that machine.