I would have both tbh, I can remember a leak saying that Apple were going for a family styled device which kinda makes sense from the video on the website, however practicalities like Facebook and twitter clients could be a problem, but I could see it used as a family device in the sense that when its not in use it is a digital photo frame, connected to a dock, when it is in use you can quickly browse the internet, put it back and be off. It would also work quite well like the O2 jongler (sp) in that you can update the calendar with important meetings/events whilst this is still manual I find it nice and simple on my iPhone and the iPad won't be much different. Also I don't know if we are the only family to do this but when we have visitors 90% of the time we get asked a question which we are unsure of the answer and so get out a laptop or run the main computer in a separate room to check the answer and this takes forever, with the iPad it is as simple as picking it up, unlocking, opening safari and checking rather than waiting for the laptop to boot up then check and you are still with visitors whilst you do this.
I think Apple haven't really sold the possibilities of this too well and are saying, its better than a netbook, just if you are a windows user, you won't know what the hell to do when it comes to doing work on it.
The iPad doesn't have to be replacement it can be complimentative.