After a few weeks, still impressed with my daughter's C720 chromebook. Groupon has these for $117 (refurb) with coupon. It pales in comparison to my 13" retina MacBook Pro, but then again, it's then 1/10 of the cost as well and I used my rMBP over 2/3 of the time at my desk with the lid closed and connected to my monitor/keyboard/mouse.
11" MacBook Air is definitely off the table.
13" MacBook Air I got for my wife last week when they had the sale and combo of student $100 off and 10% rewards (net of ~$730 after taxes and all). She uses it exclusively as a laptop and never will be docked to a monitor, but for her use and eyes, that 13" MBA is absolutely perfect.
As for the iPad, I love my retina Mini iPad because of the form factor and use in bed or on a plane. Crisp display, fist in a jacket pocket, and awesome battery. From an app standpoint, the iOS and OSX are a bit different. For my use, I "need" a tablet as well as a computer.
But this cheap chromebook is nice to have with a keyboard and for browsing/typing is much better than the iPad. Since I use Gmail and Chrome as my browser across my computers, iPad, and iPhone, Chromebook is very easy to set up and use (I have a profile set on my daughter's C720 for my use). Great battery and I'll always have an internet connection when I use it. Screen sucks compared to the rMBP, but it is the same as that 11" MBA I was originally considering.
But with the chromebook, no OSX, no iMessage, no native MS Office apps, and it's a celeron processor instead of i5. Do I need an i5? Probably not. The SSD (even though small) provides more kick than the processor. And whenever I edit photos and videos, I do it on the more powerful Mac anyway.