No, not necessarily.
My experience is not directly transferable, since I'm a graduate student. The majority of my readings are in PDF - they are journal articles in scientific articles. I use my tablet (iPad 2) to do that reading. I have an app that allows me to sync them to the reference management software I have on my Mac and keep all of my articles organized. I can also use this app to sync to Dropbox and add notes, highlights and annotations to my articles.
If I have books, they are usually widely available on Amazon.com, so I download them in Kindle format to my reader. Rarely do I have textbooks anymore, but some textbooks are available in this format. Kindle is also useful for outside reading that's not required - for example, they have a lot of the statistics books I use to teach myself new concepts. I also read for pleasure through my iPad.
I also use my iPad to read the news so I don't have a million newspapers lying around. I've got tons of new apps. I also use it for casual web browsing when I don't feel like bringing my Mac somewhere. I have a portable keyboard I can use for it, so it's useful for taking notes during short meetings for which there is no point in lugging my Mac. Especially with Mountain Lion coming out, it'll be easier to sync my notes across the cloud.
You have to think about what your needs are. If you have a thin and light notebook like a MacBook and you aren't going to be reading a lot of PDF files, then you probably won't have much use for a tablet.