I first saw Donnie Darko on DVD maybe a year ago. This Director's Cut re-integrates the Deleted Scenes I saw on the DVD Special Features, so there were no surprises, just a more fleshed-out film. I still find Donnie's sleepwalking encounters with Frank very scary, but the whole movie felt more pretentious this time around.
It's funny- Donnie Darko was not a success in theaters, but has gained a cult following on DVD. That means more people have seen the DVD (and have had the opportunity to see the Deleted Scenes) than only saw the original theatrical run. Usually people who watch a Director's Cut are seeing some footage for the first time, but I'm guessing the majority of viewers at the Brattle had already seen the extra scenes on the DVD. Way back in the early nineties, when Blade Runner was released as a Director's Cut, it had been released on laserdisc but I don't think the Director's Cut was released on VHS? I'm not sure.