What are some good writing tablets for taking notes that are heavy on math/physics? For the record, I'd like something to replace notebooks. I'm accumulating more and more notebooks, and they're a pain to tug around everywhere. Plus, notebooks are easy to get lost (I've lost notebooks by accidentally leaving them in restrooms), not easily-backup-able, and non-searchable.

So I'd like a tablet that allows me to read PDFs heavy on math/physics, that allows me to easily annotate notes, and that has a thin stylus that allows me to write subscripts and superscripts with ease.
I believe the limitation is more on the software that you are using, rather than the tablet itself. So, if you are using an iPad, you can use UPad, whereas android tablets users should be looking at something like Repligo or ezPdf Reader.