As above, just been asked to update.

will prob do mine tomorrow, cheers for the heads up

This is what seems to be in the new update. Probably some more but this what i've found from other sites anyhow

This update prepares for the 17th December release of PlayStation Vita in Japan.

Firmware 4.0 enables PS3 to act as a content hub for Vita. Things like games, music, photos, videos and save data can be shared from Vita to PS3.

You'll be able to use the PS3 to update firmware on Vita as well according to a PS blog

Other PS3 firmware 4.0 changes include PlayStation Plus offering automatic updates for game patches, system software, sync trophy information and recommended games and videos.

There are new, unspecified PSN privacy settings for filtering friend requests and messages.

Those are the announced features of PS3 firmware 4.0.

The unannounced features of PS3 firmware 4.0, according to Just Push Start, are the ability to delete Vita system backup files, a enw PS Plus icon on XMB, remote play settings for Vita and a Vita applications folder on XMB (in the Game menu section).

wonder if those tru blue dongles still work with the games that'll start requiring 4.0 and whether this'll be jailbreakable with the same unreleased methods we've heard about with 3.73?

Just updated now. Seemed to whip through the d/l and install. Can't imagine its a sizeable update.