Well, I've been living with the No. 585 for four months now, and thought it time for a brief update.
The only amplification I previously owned that has similar power output capability was an Adcom GFA-555, which was let down (imo) by the GTP-550 preamp I had paired with it (most buyers of the power amp likely used theirs with a different brand pre). The 585 impresses with its output capability, and even more so with its finesse. SQ of this integrated bests the Adcom pairing easily. As well it should, given the ask.
Which means that this is the best-sounding amplification system I've ever owned, but better than that, it rivals the best I've ever heard, which was an ARC SP-11 preamp with a pair of M300 tube mono-block power amps, a $15k rig 23 years ago - driving Duntech Crown Prince speakers, it was a system I used daily for months. The ARC probably sounded better (aural memory being what it is, and aging ears are just two factors that muddy the waters) but the 585 certainly reminds me of that time, and that sound. This makes the ML my reference amp, my benchmark.
Now I have a confession to make. When I anteed up for this costly beast (I know, cost is relative, but few enthusiasts would think the $12k new price anything but costly, and more than half that for a slightly used one still nothing to sneeze at), I certainly hoped to get what I think of as high-end sound quality, and am very happy with that, but the second-biggest reason I finally decided to spend so much (an exorbitant amount for me) was my infuriation with user interfaces of everything else I tried, or considered.
I was purely sick of motorized volume pots specially designed to make it impossible to see their settings from across a room, and even worse, digital displays too small and/or dim to see from that distance. One can pretty easily find a brand new alarm clock that can be easily read from twenty feet away, for less than twenty bucks - less than ten with a bit of persistence. But audio gear with bright, legible displays requires thousands of dollars for those with poor vision like mine. The ML's red LED (I guess that's what it is) may be a little old-fashioned, but it is big, bright and easily read from my seat about fifteen feet away.
Control-wise, the 585 requires one to scroll through inputs (in either direction, endless loop) for selection, but does allow the user to delete unused inputs, which helps a lot. The volume control is exemplary, with 0.1db steps - yes, a tenth of a db. So fine a range that it doesn't sound like discrete steps at all. It takes growing accustomed to the timing of how long to depress the button - not long. It begins slowly, then rushes upwards. Easy to get surprised with very loud music until you get the feel of it. They could have made the faster rise a little slower for my taste, but time has shown this to be only a minor annoyance initially, which becomes a non-issue with use. OTOH, I certainly would not hand the remote to just anyone, without explanation. Some wouldn't qualify even with explanation.
And that's about it. I choose the input, I set the volume. Other than initial set-up, those are the only controls I use. I assume the bass and treble controls in sub-menus are functional, but all I've ever done with them is check that they were set for zero boost/cut. They were and still are set that way.
I get great sound at low levels or high, with a muscular sense of ease. Detail, imaging, deep bass - all of its attributes. A powerful amp that sounds good with the first watt, imo, and when turned up merely gets louder with no change in character that I notice. I'm hitting around something I can't quite put into words here, but the presentation speaks for itself when heard.
So, yes, I am happy with the purchase - and that is understatement. It's worth the price. I don't regret a penny. As long as it continues to work well, I'm highly pleased. I no longer wonder whether I'd like Brand X better, or become annoyed with the amp I use. It has become the foundation stone for my entertainment system - a trusted reference. If it begins having functional issues, I'd get it fixed, sell it, and remain mid-fi with an affordable low-price Yammie or Marantz, deciding that I can't afford to drive a Ferrari. The shipping alone would cost about as much as an AS-501, I think.
I like the clear, crisp click of its relays with turn-on, or when simply switching sources - heard easily across the room (not through the speakers). I like that when you turn it on, the display reads "Mark Levinson" for a few seconds before reverting to the normal source and level information. Most of all, I like the sound. No, the display! Yeah, the sound! Display! Less filling! Tastes great!