There are 2 Palettes (3 actually if you count the single input version) - the legendary and expensive Cello Audio Palette MIV and the more home-use version the Cello Palette preamp. If memory serves, the Stereophile article (read it moons ago) is for the consumer preamp and most of the studio engineer discussions refer to the MIV. Easiest visual distinction is the knobs and the size of the PSU, but the bands controlled are also different. The MIV has pots for 15hz, 120hz, 500hz, 2khz, 5khz and 25khz whereas the Palette preamp has pots for 20hz, 120hz, 500hz, 2khz, 5khz, 20khz – the latter is much more useful tbh as I’ve never really yearned to boost anything lower than 20hz or higher 20khz.
Most importantly, and what the article speaks about, is that not all recordings are the same - this is so important to me personally because I have very large variety of music that falls outside of what most audiophiles consider well produced, and I view all art as a spectrum like that. Some of the most amazing music I own is some of the worst produced, but there is an undeniable magic contained in there. Also, unless you’re listening to music in a vacuum, there is over a hundred years of advancement in the artform and while I have different cartridges and a couple amps that try to keep things somewhat "period-correct", there will never be gear that averages everything perfectly, and even if there was that’s probably not ideal for the margins of the spectrum. So, I find the Cello a very useful tool in accommodating my variety of listening, the key is to boost or cut things in moderation, a pinch more cymbal sizzle here, a pinch more guts in the stand up bass there, or very subtly taming a bit of glare. It is not a "loudness" switch.
In terms of sonics, I will say its bone-dry neutral verging on analytical, which can paint very vividly, but admittedly there are times where I do need something more forgiving and switch over to my tube pre.
What I will say is a pain in the ass... is yes, maintenance. I had a DC issue on one channel that required some parts to repair, and as you can guess with Levinson, the parts are somewhat proprietary and unobtainable, Vishay was no help therefore I’ve been in over a year having to create a couple replacement parts. But that said, I scored mine for a very very good price so this repair isn’t hurting my soul too much.