I purchased a 20057 off of ebay for $615 shipped. My main goal was to have a superior mulcher that my fiance would enjoy using. I waffled between the 20055 and the 57 for a while, then decided to splurge. I'm sure I'd be happy with either though as they are the same, except for the engine.
I do not consider this to be a light mower, but it is very well balanced. The only time you realy feel the weight is if you have to lift the entire mower. It does not start on the first pull when cold, but always starts on the second and requires only enough pull to get the motor spinning. You don't have to yank on it. When warm, it starts on the first gentle pull.
I really like the personal pace system. You simply forget it's there. You just walk and the mower stays ahead of you. I do believe that a mower in this price range should have a blade clutch. You can get that with the 56 or 58, but you can't have the Intek with the clutch.
The mulching is simply phenomenal. It does not bog at all in my thick St. Augustine, and the clippings are not visible except on the sidewalk and driveway, and even then they are very fine and blow away with a good breeze. I was tired of either having clippings kill patches of grass or having to bag them and watch my fertilizer go out with the trash.
I could have saved some money by going with a push Super or the Recycler(Non-Super) but I knew my fiance would not use a push mower, and I wanted the higher quality drive components of the SR as well as the aluminum deck. The deck does not make the mower much lighter, just rust-proof. The difference between a steel-deck Recycler and an aluminum deck Super is only 2 pounds. Not enough to matter.
My fiance simply adores the mower. She had tried pushing out old Murray aroud and simply was not up the job, but can handle the personal pace 20057 with no problems. She also has no problems starting, except when she forgets to prime it when cold.
I did encounter a problem right off. The left wheel over-run key had sheared off and left it with one wheel drive. It did not effect the operation of the mower except when going through a patch of wet grass, when the right wheel would spin. Otherwise I'd of probably not noticed it. My fiance never did. The key was $4.10 and took 5 minutes to replace. I'm sure the warranty would have covered it, but it was a simple fix and I could do it myself easier than taking the mower in. From my reseach, if there is a true defect in the mower, the warranty will cover it with little trouble. That said, 90% of small-engine trouble is due to leaving unstabilized gas in the tank. It is unreasonable to expect a manufacturer to cover abuse.
As for build quality and reliability, I believe you might be able to do better, but not at it's price point and feature content.
I've heard some say that it is still splash lubed, while others say it is pressure lubed. I don't know which it is, or if maybe it is a mix, but what I wanted the filter for was to keep the oil clean. It will do that no matter how the lubrication is achieved.
Best mower? "Best" is such a relative term. After all of my research, I do believe it is the best mulcher. I also believe that it's mowing quality is probably near the top, if not the best in a rotary mower. It's ease of use is top-notch, requiring no instruction to my fiance, beyond that of our last low-budget push mower. The Personal Pace system is intuitive enough for anyone to figure out. Basically, check the gas and oil, push the primer 3 times, pull in the blade brake, give two gentle tugs to the starter rope, and then start walking while holding the drive handle. Stop waliking and the mower stops. Easy as pie...