Well, the iPad will be in addition to a laptop that I'll need for GIS and working together with others, so it'll definitely not be my only device for productivity. I did realize that on my 13"MBP, I did not do much more than text editing and browsing, so it's not a loss in my mind.
I'm pretty sure it was this Cortex episode that got me interested in using an iPad. I already use pen & paper as a way to get my thoughts straight but want to up my ante. Playing around with GoodNotes and Concepts already has me confident that I've made a good decision.