For me, the main appeal of the iPad was that it's a truly mobile device. What I mean by that, is that you're lucky to get 45 hours or so out of a MacBook Pro (half that if you're stressing the device with things like photo/video editing) when I easily get 812 out of my iPad. With the exception of a day when I spend a
lot of time playing games (usually
The Pinball Arcade,
SpellTower, or
Ascension) I basically never have to charge it during the dayI get a full day's use out of the device, unlike a MacBook Pro where I would always have to plug in at least once.
It's also considerably smaller than any of the MacBook Pros, which helps with portability. Most of the time I was just moving my MacBook Pro between desks, rather than actually using it as a mobile device. And if you compare it to the 11" MacBook Air, which is the closest thing in size to an iPad, the battery life is
significantly better. (the MacBook Air battery life sucks) The MacBook Air also requires more space to actually use, even if the footprint is similar, and with no retina display, text doesn't look nearly as good.
It's a
great reading device. We do now have a Retina display available on the MacBook Pros, but only at 15" and you have to use them in a landscape orientation. I much prefer being able to hold the iPad more like a book or a magazine in the portrait orientation and read text that way.
It's significantly cheaper than a MacBook Pro. My computing needs are quite demanding, and so I found myself wanting to upgrade my MacBook Pros on a yearly basis. Even when selling the old one, upgrading was a significant expense, especially if you buy the top-spec machine rather than the base-spec. With the iPad there only is one spec, you just pay extra for storage if you want it. At $500, it's cheaper to buy a completely new iPad than it was to upgrade my MacBook Pro. That's what I did this year, so now other family members can have use of my iPad 2. For my computing needs, I built a desktop PC about 18 months ago, which cost about half the price of a 15" base-spec MacBook Pro at the time, and is still faster than any Mac you could buy today. I won't have to upgrade it for at least another 612 months (I'll probably wait until the next lot of Intel processors come out) and even then it will still be a lot cheaper, as I'll only be replacing a motherboard & CPU. (I spent a bit more for 16GB of low voltage, high speed RAM so it won't need changed)
It's a much better gaming device. While the MacBook Pros can play "big" games, they don't really have the graphical power to play them well. 30fps at best in most cases if you are running at native resolution. (this has always been the case, not just retina) With the iPad, games are made specifically for that device, and the games for it are much better suited to gaming on-the-go anyway. I have a desktop PC now for all my computing and gaming needs, which bests the MacBook Pros by a significant margin. There's a lot of great board/card games being brought over to the iPad, and they're great fun to play with family/friends, and much more convenient than physical board games. You can get a game of
Ticket to Ride done in about 15 minutes compared to an hour or so with the "real thing" for example, and most games support play between multiple iPads and/or iPhones/iPods.
I just generally like the "appliance" nature of the device, and flexibility the touchscreen provides. While the music creation tools like
Korg iMS-20,
ReBirth, or
Animoog may not be as fully-featured as desktop software, I would never have bought desktop software for that to begin with. Instead I can pick up tools like this on sale for less than $10 and actually get interested in that sort of thing and create music. Or I can pick up a great sketching app like
Procreate and start drawing again.
I prefer writing on my iPad, whether I have a bluetooth keyboard synced up or not, because it's a single-tasking device so there are no distractions like there are on a computer. I can't just CMD + Tab to another app to read my mail, browse the internet etc. It's not difficult to do on the iPad, but that extra barrier seems to be enough to keep me focused on the task at hand.
And even just for things like browsing the web, it doesn't feel like I'm using a computer. When I'm working, I'm in front of a monitor at a desk all day, but with the iPad I can be leaning back in a chair or lying in bed without a keyboard in front of me. Even if I'm just reading forums (or posting to them) it's a much more relaxed experience.