Steam, you had better spend the next few days enjoying it while it lasts. Valve has announced that after two months in beta testing, their new user interface and features for Steam will officially become active on Monday, April 26.
Valve termed the Steam UI beta to be "a huge success" saying the numbers of user that opted to check out the beta "xceeded all our expectations" (specific numbers were not revealed)". You can still choose to test out the Steam beta now. It will not only give you a head start on the new UI it also will minimize the amount of updating the Steam client will have to do on Monday when the user interface officially goes live.