I would primarily use it to do research. I create powerpoints, however I know that the device is only good for viewing files not creating. But if its more like a large ipad touch then I am not sure if one is for me. I hear there can be eyestrain by using one due to the backlit screen. I do travel a lot for work, but they are day trips where I drive. So using it to watch movies on the go is no really an option. I am seeing if anyone can tell me features about the ipad that would sway me to get one for my use.
It's really a tough call - and in many ways, the iPad really is just a gigantic iPod Touch.
I do agree with lifesabeach that the Kindle makes a better eReader. It really is like looking at paper, whereas the iPad is much more like a typical computer screen - and the glare can be really tough to deal with (not much of a problem with the Kindle).
I bought a new MacBook Pro in late February, just a few weeks after getting one of the Verizon iPhones. In April, my company bought me an iPad 2 to experiment with so that I could support it more effectively in our environment. I find that I use the iPad very infrequently - it's just not all that useful for content creation, or even participating in forums like this one. In terms of using it for presentations, it can be a pain to get documents onto it, and of course, Powerpoint is not made for the iPad (although you can get Keynote for the iPad, but I haven't seen the degree to which the iPad version is compatible with PP).
Ultimately, if you have a laptop and a Smartphone, I'm not sure that there is a great need for something in between. I guess if it's your first exposure to iOS and the App Store ecosystem, it might be a lot of fun. But it might make more sense to get a dedicated (cheap) eReader to compliment your existing laptop, rather than trying to replace the laptop with an iPad, which is not really a good laptop replacement (IMO).
Hope that helps.