I was teaching my fellow junior consultants not to have an open laptop while in client meetings.
Psychologically, it was much better to have a nice medium-size notebook such as Moleskin and a quality pen and to listen attentively to the client while taking notes, even if that was a poor courtesy.
Putting a laptop between yourself and the client and typing on is borderline, or even outright, offensive unless you can touch-type and look the client straight in the eyes.
With the advent of tablets, you can take notes, but as long as the display is visible to the person that you talk to, it is very acceptable.
