My iPad usage has INcreased over the last few months. It's with me 24 hours a day, and has eliminated my need for a laptop; in fact I sold my laptop shortly after getting my iPad 2 and haven't missed it yet. I wasn't doing any heavy lifting on my laptop, and for the rare occasion that I need to, I still have a machine at home that serves that purpose (maybe once a year tops).
I have also been re-reading some old books lately, but have been reading them on my iPad. We are trying to sell our house and completely removed an entire bookcase full of books and magazines to reduce clutter. Another thing I haven't missed yet. Yes, I have to pay for the books, but I only get through about one every 1 or 2 months and it's one less thing I don't have to carry in my backpack.
My Xbox 360 and PS3 usage have gone down dramatically. I'm gaming a lot on my iPad lately. Nuff said.
One more thing: as a chord cutter, I find the iPad to be terrific. I use Hulu Plus and Netflix on my Roku box, and have both apps on my iPad as well. Because of this, I'm doing more of my TV viewing in bed. It eliminates the problem of me falling asleep in front of the TV and then waking up and going up to bed. Instead, I put the iPad down when I get tired, and I get more uninterrupted sleep at night.
Because my iPad (and to a lesser extent, my iPhone) have freed me up to do more things away from where I usually do them, I find my usage increasing all the time. Now that I've learned all the ins and outs of GarageBand, I will be on it even more.