For me, the most interesting about Tim Cook's post was this : "Just imagine all the things it’ll be used to create."
In the context of technical or engineering content, my feeling is that the iPad is primarily used to consume content, not create content.
Since I'm not an "artist" in any sense of the word, I don't feel qualified at all to comment on using an iPad to create "artistic" content, but it's very hard for me to imagine a scenario in which almost any part of technical content creation would, or even could, involve an iPad, except maybe as a video recorder.
Making it thinner does have an advantage in terms of content consumption in that it would be even more portable, especially for the larger (13") iPad, but I think I would also trade a couple of extra mm for a much longer battery life.
I absolutely love my iPad and use it constantly, just not for technical content creation.
Edit: It's also worth noting that one's choice of case can easily double or triple the thickness of an iPad. I actually find it easier to manipulate my iPad when it has a thicker case on it.