If you only use it on wifi (like I do), there isn't a data fee.
I love my iPad and used it all through school for taking notes and everything. It's not a standalone device - you need to have a real Mac as well, but if you already have a Mac in the house, you'll be fine.
I love my iPad. It's great for travel and for reading and for taking notes and for the fun apps which are unlike anything else. I really wish it wasn't a closed system so I could program on it, but other than that, it's really fun. I'd totally get one if you can afford it.
If you're just looking for a reading device, I highly recommend the Kindle. If you're looking for a real computer that's highly portable, but still a real computer, I recommend the new macbook Air, which is what I'm typing this on now.