It seems the first few (mainly free/cheap) festival shows have started selling out already. Of the main programme, here are my suggestions.
Koyaanisqatsi. Great film and here you have the chance to see Phillip Glass conducting his own work.
This Is Pure Scenius. This is probably the "experimental" music hi-light of the festival. Eno, the Necks and the bloke form Underworld jamming through three sets over the course of a day.
dreamthinkspeak: Before I Sleep. A sequel to Chekhov's Cherry Orchard and enacted in the old Co-Op building on London Road.
Seeing Things (A One-on-one-Experience). Your entrance fee buys you five "one on one" performances. That's shows where there is one actor and one audience member (you).
Marine Parade. Going on in a Brighton bed and breakfast. Featuring songs by the American Music Club's Mark Eitzel