I travel a lot for business, generally several flights a month. Last week I made my 1st ever trip with just my iPad, leaving the laptop home.
I really did not miss the laptop (much). Yes, there were a couple of times when it would have been useful at night in the hotel room, but not mandatory. I did pack an Apple Bluetooth keyboard and used it in the hotel room for email composing.
It should be said that the vast majority of my work is email based. So the email and web browser apps get me through most of the day. With Dropbox, Numbers, Pages, Keynote, and a few other apps, traveling with just the iPad was plenty sufficient.
The added advantage of passing through security without having to pull the laptop out is nice (I know it is minor, but it is in fact a convenience). And even though I have a small/light MBA + charger, saving that 3 pounds is nice on the shoulders. (Note that I would have taken the iPad even if I had taken the laptop.)
As for around the house, I use the iPad nearly exclusively over a laptop.