I only use JRiver for audio and I haven't upgraded for a while as I haven't seen any audio enhancements I want to use. JRiver is one of the most rich apps for audio but there are some things that I think would make our user experience so much more simple and rewarding. Here are some of them (apologies if some of these exist, are simple to use, and are in an obvious place already):
Reporting
A simple reporting interface, such as mysql. I know it's possible to make lists but it's not simple (filters quickly become complex and messy). I'd expect some canned reports, such as author, album, and ability to export as csv. One simple use case would be when I'm browsing for new albums, I always wonder "have I got this already". Getting a unique list is very tedious even with pretty good older structures when you have 1000's of albums and a poor memory.
Equalisation
An equalizer with a lot more than 10 bands. I know I could define parametric eq but it's too much trouble and most people don't understand how to use it.
Ability to turn equalizer on/off from the main browser (instead of hiding it under options).
Ability to select equalizer presets easily in the main browser. Automatic selection of the eq preset based on genre.
Standard list of genres. Help with selecting genres (for those of us that don't want whatever the media source decided).
Internet Radio library in JRiver. I used to love squeezbox ease of browsing thousands of internet radio stations. I don't want to be forced to discover online radio stations (using some other product) and enter the url to JRiver (or remove it if the url changes).
Gizmo
It's a great tool, but I hope it can be made easier to use and gain some extra functions too.
Ability to navigate on mobile devices using touch screen (swipe). It's frustrating to go back from the player page to the track list or album list and there's no way to go back where you were.
Equalizer functions I mentioned above should be available in Gizmo too.
Ability to select to list artists/albums in a list not just icons.
An exit key! It's painful backing out of Gizmo page by page and having to kill it in task a manager.
Ability to read artist history, discography, descriptions, etc, and browse through my collection like on allmusic.com would greatly enhance the listening sessions. I often read allmusic.com while listening to music using gizmo but integration would be amazing.
Ability to use additional metadata sources like freedb for metadata tagging.
Ability to rename ripped cd files using metadata sources, eg freedb
Ability to use gizmo to browse and play my collection when I'm away from home. Jplay requires me to use a static ip address for the server but that's not practical/possible these days. All my local telcos assign dynamic ip addresses.
I'm sure to have more wishes tomorrow too ;-)