By having a decent sense of perspective, and being able to distinguish things which actually warrant the slightest bit of care from those which don't? (oops, I meant 'fanboy', rabble rabble)
Complaining about a 5 second boot time because 'it's not instant like they said'. Wow. I've seen it all.
The only thing I'm complaining about is the amount of blind acceptance in a product that doesn't deliver what was advertised. Hell, I experience this all the time with my MBA, and it's STILL leaps and bounds faster than any other Windows machine I've ever owned. I'm confident in saying that I never would have bothered to come on here and ask this question if it were just me - but I can absolutely see why someone would question Apple's claim. It's as simple as 5 =/= 0. Now obviously instant is a relative term, but in this case Apple made a direct comparison of this boot time compared to their iPhone and iPad, which do wake up from sleep instantaneously.
If you don't think the difference between 5 seconds and "instant" warrants any attention, then so be it. But it's pretty impressive that you're so taken back by the fact that someone would question that.