I've been using Panel for a few days. (MC on Mac, Panel on iPad.) It works pretty well for the most part. Two things are keeping me from converting from JRemote to Panel:
1. Showing artists and albums only in icon view doesn't scale well. With 1500 artists in my music library, it's not really convenient to scroll through all those icons. A list view would be much more useful (and speedy) for me.
2. On a related subject, the slider at the top of an icon view (e.g. artists) doesn't seem to work properly on my iPad. For one thing, using the slider to slide down to somewhere way down the alphabet usually results in the display only scrolling down a page or two. E.g. slide to "M", and the second page of "A" is displayed rather than "M". This doesn't always happen, but it usually does. But more seriously, th slider only is visible when viewing the very top of the (sometimes) huge list. If I scroll down to the "M" part of this list, the slider is not visible. And there is no way to get it back other than scrolling back up to the top of the list. With 1500 artists, and no scroll knob or any other way to get to the top, this is just not usable.
Also, the slider isn't visible in all screens which show a bunch of items. Drill down to Music > Genre > Jazz, and you get a list of artist icons but no slider. The slider only seems to be implemented at top-level lists (Artists, albums).
This is MC 24.0.53 running on macOS 10.12.16, with Panel on an iPad running iOS 12. Both machine on the same local WiFi net.