Comparing MacBook Air sleep resume times Q1. Which MacBook Air models have the fastest resume-from-sleep times?

In other words, how long does it take (in the most common scenario, not the theoretically-shortest) between opening the display lid and getting a keypress echoed in an open TextEdit window?

Q2.  Do the newer (or newest) MBA's have faster resume time?

Q3.  How does this compare to the resume time of the iPad?

For the purpose of these questions, milliseconds matter!
This is not an actual answer to your questions, but more information on the subject:

MacBook Airs go into "deep sleep" (hibernate) when left with the lid closed for a longer while. Basically, the current state of the machine is saved to the hard drive (the SSD in the case of MacBooks) and the machine turns off, thus not consuming any power while in standby. When you open the lid, the machine state is retrieved from the SSD and restored.

So, the wake time is determined by the speed of the SSD inside the MacBook Air.

2010 MacBook Airs have SSD speeds in terms of 100 MBps, while latest MacBook Airs (2012) have SSD speeds in terms of 400-500 MBps, so wake time should be a lot faster with the 2012 models.

Comparing with the iPad is irrelevant, as iPads do not hibernate, as far as I'm aware of.