Repeating some UX suggestions as a vote for them, plus additional:
+ Left column tree, ability to hide/show most or all of the items, at their top level and/or sublevels. It is cluttered with things I don't use, but others would desire a different mix; let us customize. But with this change, provide a straightforward way to show the entire tree, then revert to the prior hide/show mode.
+ Customizable right-click would be wonderful, and/or expand the number of Recent items. (It would be interesting to know what everyone's Recent items are, in case there's a pattern that could help MC better organize the fixed right-click options.)
+ Do not auto-expand Playing Now, I've never found the things it exposes to be useful at that time, it just clutters the left column.
+ Allow more customization of menus and toolbar and the like, to further improve user efficiency. For instance, the Action Window has a bunch of actions I never ever use (used to, but not anymore), yet my brain must scan the long-ish list to select the one item I want. Let the user choose what actions are in the Action Window, presuming everything else continues to be in the menus. Which raises the point, why does the top menu not have an Actions item that contains the same things as the Action Window menu?
+ How about more consistent organizing and labeling of menu options? At least a few things are not where expected, either given different names, or suboptions of other things that require experience to discover and remember. For instance, Player > Display Options offers a bit of control over how Cover Art images appear, but that's all. YET, there's a lot more display to control while playing a track.. but how? The same Player menu also has Playing Now and Playback Options, which seem useful but do NOT provide control over what is on-screen while playing (huh?). It likely takes several clicks to determine what is controlled in these three sections of the Player menu. But gets worse, because several major Playing Now / Display settings are usually hidden, with no clue they exist, unless Display Options is improved.
+ With Display Options as an example, improve placement of action/menu items that (oddly) only appear within other things, otherwise being not useable or even findable. EXAMPLE: How to control what is shown during playing now, while a track is playing? Very obscure to control. Seems like Player menu item Display Options might do it, but it just provides diddling with Cover Art image. BUT WAIT, THERE'S MORE: Play a track and essential display options appear -- but only while a track is playing. Stop the track and they disappear again. It takes luck to click Display Options while actually playing and discover the wonders it usually hides.
+ Add UI options for Images Only and Video Only to the current Audio Only mode. Not having this makes MC much more confusing to learn and use, because inappropriate things are not obviously inappropriate, and sometimes lead to unwanted outcomes. And, since MC already provides Triple Value (there's a marketing bullet point) by handling the three main media types, why not make it simpler to cleanly use them?
+ Support PDF as a fourth media type. Having straightforward support of PDF organizing, viewing and tagging could be a big big attraction in business contexts.
+ Allow Tag window to be floated -- and/or provide a separate floating, resizable tag window that can be opened and kept open as the user desires. This has been requested forever, so likely it is not easy, but perhaps there's a compromise? Expanding the fixed tag box is not ideal, because it requires extra clicking to open/close, and because sometimes the need is to see wider fields as well as more fields.
+ Allow font control in views, at the row and/or column level. Not all columns/fields are of equal importance to the user, it would be nice to do things like show song names larger, artist names in bold, certain fields in monospaced font -- whatever the user wants.
+ Allow customized view layouts to be interchangeable among ALL view-type screens, to save and re-use in any type of view, whether user-created or built-in or generated by MC or whatever. It is crazy to get a view all tweaked up then have to do it again and again, with built-in views at some point discarding the user changes.
I don't know what is "simple" for JR to implement, but helping current and new users seems desirable. I'm watching the current rebirth of WinAmp, which claims to have the largest world-wide user base, and promises all kinds of UI and features improvements. It might be a new ballgame...