Simple to use once you realise that there is a setting on the camera that must be set first! There are no instructions with the product so you need to know this from elsewhere, like here! Turn on the camera (D40), press Menu button, select (in the left column) Custom Setting Menu, move to right column and select Shooting Mode, select 2s [second] Delayed Remote or Quick-Response Remote. This setting is only valid for one picture so you need to reset it for each picture. I think this may be to avoid conflicts with other cameras in range - you don't want them going off at random just because someone presses the button. That should save you some time.
The only problem is with the camera rather than the button - the infra red sensor is in the front of the camera (mine's a D40) so you can't be, for example, hidden behind the camera while waiting for that damned bird to stand in the right place!