I'm 50+ with an 11" Air and I do find I need to wear my glasses EVERY time I use the Air, but that's about it. It's simply the most portable (full) Mac. iOS and touch is
delightful, but for not much extra size or weight, you get a much more powerful computer.
I bought it for typing and general internet, but I've used it for so many thingsaudio recording & editing, non-professional video editing, even some photo editing. I had it simultaneously ripping and converting Blu-rays on the weekend. It gets the job done with very little fuss, even if it does strain the 2GB of RAM. Totally awesome Mac, at almost iPad size. Just Brilliant!
The screen size is spot-on for portability. If you want more screen, you can always get an external monitor. Could definitely use more pixels though, as long as it keeps the 16:9 aspect ratio, as it matches the human field of vision better.
Also brighter and more colours, especially when on-power, wouldn't hurt. Guess I'll be waiting -another- year for a better display. Hurry up Apple, the 2GB RAM it has is straining at times.
It could (like all Macs) benefit from Touch, like iOS, more intimate and direct for on-screen elements.
I can see a day when all Macs lie down on their backs for touch, and just have an aluminium chin, like the iMac for a wrist-rest. 27" down to 11" slabs, the 'line' moving from desktop to Mac Book seamlessly.
Doesn't leave much room for an on-screen keyboard on an 11" Air, but I guess for serious typing, I'd get a keyboard anyway. A small chin on an 11" Air would change the (beloved) footprint significantly, but if it were thinner, that might make up for it. I do like the full metal clamshell for protection, but I'm not a designer, that's their job to solve.
Great Mac, best size, even for the inconceivably old
Glasses are a small price to pay for the portability.