The DCT will have some shifting lags now and then. Although the shift itself (one clutch engages and the other disengages) is pretty quick, the next desired gear at the other axle must be pre-selected right in order to avoid delay. For example, when you are accelerating steadily, the gearbox will pre-select the next gear in the other axle and shift into it eventually, etc.
However, there will be situations when the gearbox can't guess the next wanted gear right, for example when the accelerator is suddenly pressed hard, so the gearbox was anticipating to shift up but now there's need to shift down. At this situation it must first pre-select that lower gear before shifting into it, which makes some delay. Or if you approach an intersection and almost stopping, and then pressing the accelerator, the DCT may be reluctant to pre-select the 1st gear if you don't stop completely.
When test driving the DCT, I recommend to test that kind of situations what it will do. It may be annoying if there is a lag and then sudden lurching because you instinctively give more foot because of the lag.
