I got my iPad Air this morning a little after 9 a.m., and while I tried to gather some first impressions about Apple's new, lighter full-sized tablet while at the office, I really needed to retreat home to put it to the most important test: How does it work when I'm sitting on the sofa in my living room?Most of my questions about the iPad Air are about its physical dimensions. I'm less worried about the A7 processor that powers it--I have no doubt it's going to be the fastest iPad by a vast margin and the fastest iOS device yet by numerous measures. But the ergonomics fascinate me. How much does shaving a little less than half of a pound off of the previous iPad matter? How much does narrowing the iPad by seven-tenths of an inch change things? Does holding the iPad Air feel more like the ultra-light iPad min
