A defeat or victory for pollsters?

In contrast, there is a perception that pollsters did a smart job for the just-concluded Delhi Assembly election - perhaps because the opinion and the exit polls mostly predicted a victory for AAP.

Psephologists around the world have produced several disastrous poll predictions in the recent past. For example, in the 2015 UK election, the average in the final stage of opinion polls resulted in 279 out of 650 seats, which is 42.9 per cent, to the Conservative Party, and 269 seats, or 41.4 per cent, to the Labour Party. The actual outcome of the election was 316 seats, or 48.9 per cent, to the Conservatives and 232 seats, roughly 35.7 per cent, for the Labour. 

Again, the 2009 Lok Sabha election is regarded as an example of a monumental blunder of exit polls