Though tickets cost ?34 a night you get a lot for your money. Set in fantastic grounds (old Belgian buildings modernised and brand new stylised architecture either side of the music) and with serious organisation the festival is a small gem in Belgium's musical landscape. Just outside town, about 10 minutes walk from St.Peters train station it's also very easy to get to.
The actual festival is more of a string of nightly events, as such there's less of a "festival" atmosphere and more of a dress-up, night out crowd. With tables and chairs set out on grass, amongst a few trees, under large covers and a choice of Belgian beers and international foods the Gent Jazz Festival still has a pleasant social atmosphere.
The music is fantastic. With headliners such as Damien Rice, Melody Gardot and Rodrigo Y Gabriela the festival manages to offer more than Jazz. Rodrigo Y Gabriela were especially amazing - backed up by C.U.B.A their set had the whole of the festival dancing.
Overall the Gent Jazz festival is expensive but quality, it's unlikely you'll regret spending those few extra euro.