Depends. I use my iPad for the following:
1. A portfolio, using the Portfolio App for iPad
. It's more portable than my print portfolio, can have many more galleries and photos, can be customized quickly for a showing, and looks great. No, not as great as my print book, but the iPad is always in my bag.
2. A general laptop replacement for email, web, etc., when I don't need a full size laptop or a "real" operating system. Easier to take notes, deal with email, and (especially) read content on the larger screen. Much lighter and smaller than a normal laptop.
3. To download, edit, and transmit news photos on deadline from any location where I can get 3G or Wi-Fi. This is pretty specialized, but using Filterstorm Pro makes it relatively pain free.
Now, a strong argument may be made than an 11 inch Macbook Air is better than an iPad for much of this work. It's faster, has a real keyboard, runs a more useful operating system, and can run Lightroom, Photoshop, and Photo Mechanic. If I were spending my own money, I'd probably go this route. But the iPad was issued to me at work, and I've been happy with everything it can do.