In no special order:
Reading iTunes or Kindle or Nook ebooks. I have a Kindle Paperwhite and a Nook tablet, and they're both nice but I generally prefer reading stuff on my iPad (so I’m glad those other reading apps exist). I like either the mini iPad or the larger one for reading books (or PDFs).
Breeding Pocket Frogs, of course. My eyes are a little too old to enjoy breeding them on the iPhone. It’s too hard at that scale to tell certain species from each other in the pond, like when the frog’s primary and secondary colors are from the same bit of spectrum, say green folium, or royal viola. I’m not a game freak in general, but I really like Pocket Frogs, on the iPad. I do still have a separate game going on the iPhone but I’m like 20 levels behind on that smaller device. Some of the frog colors make me sad, they remind me of real salamanders or newts that I used to see in the wet spots of my own yard in springtime, and haven't seen now for decades. It's still wet in the yard, but something about their former ecosystem has changed, and they're gone.
Reading the NYT, Economist, New Yorker. Their presentations of content are wonderful. I never imagined even in the 80s or 90s that one day I could walk around with an archive of dozens of issues of The New Yorker in a device the size of a salad plate. It's heaven on earth.
Watching purchased movies or TV shows, video podcasts and a few favorite music videos.
Reference apps - like Mactracker, WorldFactbook, the Bible, Shakespeare, Yard Bird Plus, How to Cook Everything Vegetarian. Not to mention the American Folk Art Museum's presentation of the wonderful 2011 exhibition in NYC of selections of three centuries' worth of red and white quilts in the collection of Joanna S. Rose. That thing is positively stunning.
Again, having stuff like this on an iPad is so amazing to me. I'm someone who grew up when "encyclopedia" was like 20 board feet of tomes in your living room, and they weighed probably a hundred pounds or more. As far as level of detail in reference apps: People scoff sometimes at something like the World Book app on my laptop, but I have to say, when I'm reading some history or even a piece of fiction and bump into a reference I just don't get (location, event, historical figure), that World Book usually serves well enough to meet my curiosity. I feel the same way about apps on my iPad. They may not be the full answer but they're a fabulous start.
I don’t surf the net at large very much on my iPad. For one thing I don’t feel like I have the same level of control over tracking cookies and scripts that I do with browsing from my laptops. Maybe I’m wrong and just haven’t applied myself to understand my range of options with Safari on iOS. But I also think I just prefer the larger real estate of my laptops for general web browsing.
