Depending on when you harvest, of course, it starts out as very euphoric, intense, energetic high, sometimes pleasingly psychedelic, although not as much as with the longer flowering tropical sativas; it will eventually wind down to a very enjoyable and slightly spacey buzz. If you leave it on the plant until more than half of the trichs have turned amber, you will end up with a very stoney, laughey-stupid-spacey high. It's also got a very unique taste and smell, like a licorice/aniseseed kind of thing.
post script: in my experience, Durban barely stretches in flowering, nearly all of its vertical height gain will be actual bud growth, and is well suited to a sea of green style grow, but also works well as large plants if you are willing to give it a long veg period. In veg, Durban will very obviously hit a wall, so to speak, as far as its vertical growth goest, and at that point it will simply thicken, and begin to put up a fairly even top canopy. If growing large plants, this is when you want to induce flowering. This would produce a very dense, christmas tree shaped plant with one massive middle cola and 4-6 large side colas, and a fairly impressive yield for a plant of that size.
Would LOVE to if I had an outdoor grow, but probably moving to a state too cold for pure sativas... but at that point I could at least grow under high wattage. Really want to try them if nothing else than for their alleged trippiness. I also have the issue of cat hairs occasionally getting on buds
