Bloom is a lot like glow, except that it's keyed to brightness, which produces an effect a bit like using HDR (High Dynamic Range). It adds blur and brightens the bright bits of the shot. Bloom is one of the most versatile filters so far, with various parameters to create a number of different looks. It's great for dream sequences, flashbacks, or other surreal shots, and works well in music videos.
Usual disclaimers apply: this is really early dev code, not representative of final quality, and we don't have a release date for it.