I really don't understand why anyone would want an iPad if they have a laptop and a smart phone.
To a point I agree.
At home I always use my Macbook Pro or my iPhone, the iPad (1st gen.) barely gets picked up. Out and about it's the phone.
However, if I'm jumping on a train for a long distance trip then the iPad can't be beat. The battery will last 10 hours whatever I ask it to do. If I hammer the phone, like any modern smartphone, the battery will wilt. A laptop is bigger, heavier and, again, with reduced battery life.
For kids in the car, it is fantastic. Hours and hours of video for them to watch and make their (and hence my) journey happier.
If I had to give up one of the phone, laptop or iPad then the iPad would be the one to go currently.