I have had my MS-20L for 7 months now so I though I would share my experience.
The sound does change with break in, about 70 hours for me.
Rolling the 6J1 tubes impacts the sound more than rolling the EL34-B outputs. I replaced the 6J1s with Russian NOS 6J1P-EV at 100 hours and it made a noticeable difference, a richer/deeper sound, my wife even noticed it. At 150 hours I replaced the EL34-Bs with Russian NOS 6P3S-E, which are NOT a direct replacement. When installing them I first removed the EL34-Bs, then turned the bias ALL THE WAY DOWN, then put the 6P3S-E tubes in and turned it on (the bias was at 130mv). After about 3 hours I increased the bias voltage 50mv and ran the amp another couple of hours. I repeated this each day until I got to 400mv. I am currently running the bias at 440mv. Changing the output tubes made a difference, just not as significant as when changing the 6J1s. I do not plan on going back to the stock tubes. I should note I used to be an electronics tech in the tube days of the 70s so I felt comfortable doing this. I would not recommend rolling tubes that are not direct replacements unless you can handle the result if something goes wrong.
I rarely use the remote, kind of a waste really.
I don't use the "cage" made to go around the output tubes, I like the look without it, and it is easier to check the bias voltage.
I use triode mode when listening to CDs, ultra linear mode with vinyl.
I ran a separate ground wire from the amp chassis to my Musical Fidelity V-LPS preamp to avoid grounding issues.
I really like the sound and would recommend this to anyone wanting the "tube sound" but is on a tight budget. I have heard the higher end amps like Jolida and think this has them beat if you take price into consideration.
Of course the rest of your system is also a big factor, particularly the efficiency of your speakers.
Here is a pix of my 2 channel system.