Here's my 2¢-worth.
Contemplating a tablet as a universal replacement of any one existing tool/device is unproductive because a tablet, like any device, is a mixed bag when compared in general terms. The better question is if a tablet can replace an existing tool/device for a particular type of user and usage.
Tablet for a student, as replacement for all papers in the backpack (electronic textbook availability is limited; it is not clear if the faculty would be able to find appropriate electronic material from what is available right now)?
Paper's advantages over tablet:
→ bigger page display
→ easier to flip through
→ for handwriting, sketching, and erasing, pencil is easier than stylus
→ inexpensive, can't break and no big deal to lose
Tablet's advantages over paper:
→ materials for all classes in one place; can't forget a sheet at home
→ great for collaborating with others
→ type notes in class instead of handwriting them
→ audio/visual materials as part of notes and homework
→ do research or homework during random pockets of downtime
→ work is backed up
→ access to all information -- can look up references, homework, etc
→ huge win if teachers choose electronic textbooks
Tablet (plus keyboard case) for a student, as replacement for a laptop?
Laptop's advantages over tablet:
→ bigger display
→ access to all multimedia and resource-intensive applications, on and off the web; tablets functionality is somewhat limited
→ better keyboard for typing
→ mouse is more precise and responsive than fingers on touchscreen
→ a Windows laptop is cheaper than a tablet
Tablet's advantages over laptop:
→ all-day battery life (some laptops now have comparable battery life)
→ light enough to carry around all the time
→ cheaper than an Apple laptop
→ instant-on/off (very convenient in classroom setting)
→ "flat" form factor
Good article for more thoughts on this subject:
-- Editorial: tablets aren't the 'third device' I'd hoped for... from a productivity standpoint, anyway