We limit screen time and definitely computer time. We have chosen not to have a Wii or DS or XBox.
I think too much of anything is bad; moderation in everything is our motto.
We have noticed that our kids engage in alot of imaginative, self-directed play when we shut off the gadgets. They play alone with legos and come up with wild, detailed plot-lines for their play.
That isn't to say that you can't be successful with alot of computer time on board. We have chosen to limit it.