(taking priority even over a game browser, which kinda bothers me a bit :P)
One reason why a games browser is a lower priority is that we will also soon have a WebGL version of the Unity app. In the WebGL version, you will be able to use the Unity app on the website in place of the Flash app.
Therefore, for WebGL, a games browser isn't needed since you can use the website to select the game. There are just some bugs making the WebGL port right now so it's waiting for the next version of Unity to come out which should fix the bugs.
We also want to get the mod framework out ASAP so that mod authors can start developing awesome mods, so that by the time Unity is released they'll be more developed and ready to go.
Edited 3/12/2017 04:44:07