* Complete overhaul of Steam client UI design to improve discoverability of features and to better expose all the information related to games in your library
* Complete overhaul of in-game overlay UI design to create a richer in-game experience exposing context sensitive information related to the game you are currently playing
* New game details view, presenting a detailed view of all the information for a single game in your library
* New grid view, presenting a graphical view of your game library
* New news page in the store/client/overlay which aggregates from Valve related news sites, official community groups, and third-party gaming news feeds
* New downloads view in the client, making it easier to track your progress downloading new games or game updates
* New Steam store design, including more integrated community features, improved recommendations, and improved video and screenshots viewing (and much more!)

Store details:

* New Steam store/community integration — see what your friends have been buying and playing as you browse the store
* Improved store layout, genre navigation, and genre pages, including more robust navigation per category
* Improved game detail pages, including quick link to demos, inline display of higher resolution game trailers, improved screenshot browser, and improved game recommendations
* New game-specific video page, containing all of a game's trailers in one place, now in higher resolution Flash format
* Improved discoverability of sales and discounts, including prominent shortcuts and consistent store-wide visual presentation for price cuts
* New quick-info tooltips on store home page and genre pages which allow users to read about games before navigating to detail pages
* New search filtering options- search for packs or DLC, easier to use filters for searching by price and metascore, and sort by release date

Client feature details:

* View of your most recently achieved achievements and likely next achievements in the client game details view and in the in-game overlay
* View of friends currently playing a game as well as all friends who sometimes play a game in the per-game details view
* View of related game news in the client game details view and in the in-game overlay
* Clock in the in-game overlay (!)
* User customizable categories assignable per-game, by which the various game library views can now be filtered
* Tracking of last played time for games to show in the client library views
* Sort your games by last date played
* Library list view displays larger graphic, and a new column displaying a game's Steam Cloud state
* New invites section in the friends list UI allowing you to accept or decline invites directly without going to your community control panel
* Cloud support for many non-machine specific local settings such as favorite servers
* Implemented new DirectWrite based font rendering for the client and in-game overlay on Windows 7 or Vista with both SP2 and the "Platform Update" installed. This offers improved pairwise kerning for text layout as well as better anti-aliasing of text on supported platforms.
* Display of total played time in the client game details view and the in-game overlay
* Type to jump support in the games list, grid, and game details views
* Better Steam cloud conflict resolution support, with the ability for users to choose how to resolve conflicts between machines
* Improved forward/backward navigation in the client UI, acting across various different view types (e.g., games list, to community, back to games list)
* New style and layout system for Steam's VGUI UI toolkit, enabling much more complicated flowing layouts. Skins will need major overhauls to be compatible with the new client, but will also have much more power and flexibility available to them via the new .style and .layout files used in the new VGUI code.
* Backup/restore wizard
* Community: all official game avatars in one place, linked from your edit profile page
* New outer glow effect supported when rendering text in VGUI
* Support for alpha blending of gradients and text in VGUI
* Support for many new layout and placement commands in VGUI
* Support for native drop shadow effect on primary Steam windows on Vista and Windows 7

Bug fixes:

* Improved reliability of auto-login to store and community when used in the Steam client
* Improved truncation of long text strings in many places
* Fixed the various UI states and settings to persist across client restart more reliably
* Fixed being unable to reliably delete previously added non-Steam shortcuts from your games list
* Fixed forward/backwards navigation on Community tab getting stuck on redirects
* Many small performance and memory usage improvements
* Improved sorting consistency between views
* Fixed hit areas on friend panel down-arrow affordances to make clicking on them more reliable
* You can now remove a blocked friend without having to unblock the friend first

General improvements:

* Now using a WebKit based rendering engine for the client and in-game overlay web browsing components (replacing Internet Explorer)
* Improved speed of in-game overlay web browser
* Improved search functionality on the Steam news page
* Web pages which use confirm() or alert() calls in javascript no longer break the in-game overlay web browser