Looking for a good tablet pc

I'm about to go back to school online and have been thinking that a tablet pc might be what I'm in need of, But i don't know much about them other than the obvious. I've been thinking about getting an ebook reader (such as the kindle or soon to be released nook) but both are about $250 and I've seen some slightly older used tablet's for about the same price. So the question is, which would i be better off with? If the answer is a tablet then what should i be looking for? I just need one that can browse forums fast enough as well as read pdf's and watch the occasional streaming video. Just hoping for some friendly advice, a friend of mine has been on these forums for a while and says your all good people. I'm looking foreword to getting to know you guys!