According to a recent comment over on /r/vrchat by one of the devs, the current in-game UI is temporary and there are plans in place to overhaul it by the end of this year or early 2019.
That being said, the dev team is willing to listen to our community feedback and make adjustments to the UI if they like the ideas. So I'm going to throw out a bunch of my own here.
DISCLAIMER: These are just my opinions on UI! Please comment criticisms and your own ideas.
• The hand-held menu should use icons primarily, but have small text descriptors upon hovering over a button. This reduces clutter and makes the menu easier to read.
• The hand-held menu's buttons can be condensed down into far fewer buttons, with seldom-used buttons compiled into a Miscellaneous sub-menu, (Toggle HUD, Nameplates, Respawn). If the sub-menus open on pointer-hover, then it won't increase the time required to access the desired function, while still reducing the amount of rarely-used buttons on the main screen.
• Images with gradient fades such as the existing buttons on the hand-menu have subtle, but abrupt cuts due to how Unity handles translucency. To counter this, solid shapes could be used with overall opacity lowered slightly, save for highlighted areas. The lowered opacity still allows for the menu to be seen through, but not enough to make it unusable.
• The Worlds, Social, and Avatar menus are all duplicate UI pieces!! Below I will discuss how each menu can be specialized for its purpose to be made easier to use and made to look better.
• A proper friends list could be represented with a condensed scrolling list of usernames and avatar previews on rectangles. Upon selecting a user, their information could appear to the right side of the panel. Selecting a user would NOT close the friends list panel and force you to reload the entire Social list. Instead you could click another user and view their info, all the while only adjusting the right hand side of the panel.
• The World list works very well, but their appearance leaves much to be desired. The small spaces as sub-dividers leave the interface feeling somewhat cluttered. However, this menu may be the most well-designed out of everything. The only complaint worth noting is that long world names break and cause text to float away and cut off.
• The avatar menu is nice as well, but the fact that it uses the exact same boxes and layout as the world menu with no unique optimizations for its purpose does leave a feeling of blandness. I would love to hear ideas for improvements on this one.
• Login menu. I have no complaints specifically for it other than a complaint that blankets all the menus. The aesthetic of 80's scan-lines through all menu buttons does not feel very polished. It lends a feeling of roughness to the design of buttons and menus.
• Lastly is not actually about the visuals of the UI, rather the sound. I think if the menu sounds in VRChat were a bit more 'modern' in the sense that the sounds were shorter, poppier, clickier. My reference for these adjectives would be something like iPhone or Android notification sounds. This part is definitely my personal taste, but a more modern sound design would go a long way in my opinion.
Whew... So this ended up a bit longer than I expected and I ended up making another mock-up, more unpolished this time, of the friends list idea I attempted to type out above.
The images are totally my opinion of what looks good, but I think they represent a step-up in the refinement of VRChat's menus. To the devs, please take any design choices that might strike your fancy, and to users, please suggest more ideas for the menus! They are rather rough right now and more refined menus would lead to a much greater user experience!