Semaphore (@Notcom) of Chronic-Dev Team has just updated TinyUmbrella to v4.30.04 which can now save iOS 4.3 SHSH blobs for Apple TV 2G. For those who don't know, yesterday Apple pushed iOS 4.3 update for Apple TV 2G users to fix screen flickering and incorrect color issues which popped up after iOS 4.2 update.
Although the IPSW version number is still 4.3, Apple dubbed this update as 4.2.1 on official changelog while Semaphore called it iOS 4.3.1 update for Apple TV 2G. Those who are still confused, the build number of latest firmware is 8F202 and the IPSW name is AppleTV2,1_4.3_8F202_Restore.ipsw.
Apart from TinyUmbrella v4.30.04 update, Semaphore said that he is working on a complete rewrite for TinyUmbrella which will have much better Linux support, unified device access across platforms, more elegant UI and automatic support for new firmware. Semaphore told that he is also working on his TinyPwn project which hopefully will be able to restore stock and custom IPSWs to any iDevice without SHSH blobs and without iTunes.
Update#1: TinyUmbrella has been updated to save iOS 4.3.1 SHSH blobs for all supported iDevices. Get it here