FL Studio 9 Introductory video ...

Some new FL9 features :

Sidechaining - The FL Studio Mixer 'Track Send' now has an additional 'Sidechain' mode to support multiple-input mixer plugins.

Multi-core CPU (Hyperthreading) - Improved multithreaded generator & added multithreaded effects processing.

Multiple controllers - Can now control multiple independent instrument channels, assigned by MIDI number.

Revised Playlist

Playlist track naming & icon - Tools for better song organization.

Riff machine - Automatic sequence generator tool.

Mixer now has 99 Insert tracks (up from 64).

Multi-core CPU support - Added 'multithreaded mixer' tracks processing for improved multi-core performance

New Plugins

Autogun (free) - Sonic adventure, Based on Ogun.
Sakura (demo)- String physical modelling instrument
Ogun (demo)- Additive metal simulation synthesizer
Gross Beat (demo) - Real-time, audio-stream playback, pitch, position and volume manipulation effect
Stereo Shaper (free) - Mid / Side stereo processing
Vocodex - The last word in vocoders (free with Producer Edition).