Today's Steam client beta largely focuses on improvements to the Steam Controller. Some of the Steam Controller related work includes user-definable action sets for legacy games, support for users adding extra action sets with their own sets of bindings, new controller action binding types that are not game-specific, and various fixes. Some of the new controller action bindings that aren't game specific include a binding for showing the on-screen keyboard as well as for taking a screenshot.
Today's Steam client beta also has a few SteamVR updates, support for showing emoticons in the 10ft mode, and more. All the details can be found at SteamCommunity.com.
If you are interested in the Steam Controller now that the support has matured quite a bit in the past few months, you can find it for $50 USD at Amazon.com.