I think this question keeps coming up because of that endlessly quoted dismissive phrase: iPads for consumption, computers for creation. Or, iPads are just toys, you need computers for real work.
I use iPads for "real work" as well as "consumption", and for so many other things. I still use my MBPr for Scrivener and other things iPads can't do, but iPads are my favourite tools.
They save the vast forests I devoured when I used paper for all the thinking, exploration, research, note-taking, sketching, journal-keeping parts of my work. My office walls are zen-like uncluttered now they aren't wallpapered with all that. I almost always have an LTE iPad with me, places I wouldn't take a laptop because no internet or inconvenient.
If I could only have one device it would have to be a cellular iPad. I could work around what it can't do, but I couldn't now work around what the laptop can't do.