Source - tl;dr enable test version in steam beta settings and play more reflex

This build is being deployed as a "test" version.
To enable test versions, right click on Reflex in steam and go to properties.
In the "betas" tab, use the dropdown box to select the public test branch.
Steam will automatically update you to test versions when available.
Note that test versions will often be more unstable than release versions and are not recommended unless you're having problems with the latest retail build.

Callvote is now properly implemented. Use vote_yes and vote_no commands to vote.
"callvote map" now gives a list of maps on the server. It doesn't actually fit in the console properly, but it's there.
"callvote mode" now gives a list of modes on the server.
Brightened enemy outlines (and made friendly blue and enemy red)
Names on scoreboard are now colored by team.
Reduced end of game scoreboard time from 30 to 10 seconds.

Removed over 500MB of unused assets. This should significantly improve things for people with older GPUs.
Obligatory "fixed a couple of memory leaks"
Refreshrate command now works as expected again.
Cleaned up some of the fullscreen<->windowed issues.
Significant changes to input system.
This should hopefully fix some of the input lag/inconsistency/stuttering some players have been having.
We're after feedback on how the input is feeling for people now so please give us your thoughts at @
Added a few more dialog boxes for crashes.
Added "r_decals" command. Setting this to 0 will increase your fps, especially if there are lots of exploding robots around.
Greatly increased max gamestate count on server. This should help reduce "disconnect on connect" bugs we are getting.

Updated editor's "nolight" texture to be at least a little bit visible.
ContentBrowserHack now has a search box (thanks Bonuspunkt)

Added default game binds:
F1 - Vote yes
F2 - Vote no
F3 - Ready
Added default editor binds:
T - Chat
Y - Team chat
6 - Create Pickup
Removed default resolution from game.cfg.

Mouse speed slider now goes up to 50.
Added hud_* commands with some basic settings for controlling the vote/chat boxes.
Added new crosshairs.
Crosshair style can be selected using cl_crosshair 1-16.
Crosshair color can be selected using cl_crosshaircolor 1-6
Crosshairs are stored in /game/base/internal/hud/ if you feel like creating your own.

Fixed health pickups on xfdm2
Removed lava effects that were causing performance issues on cpm3.
Included community maps submitted through the forum thread @

Known Issues:
r_refreshrate is actually still broken if you alt+enter repeatedly.
There can be a slight lag when connecting sometimes.
Players can connect and be using an axe but it will look like a burst gun to others.
There is no replay on the main menu because the replay format changed.