I share your concern, and will be able to answer next week when mine arrives. I use my laptop a lot laying back in bed... often in the middle of the night. Of all the laptops that I have had, my 2009 MBA is the easiest to use in the dark. My Alu MBP (silver backlit keys) was OK... but not as good as my MBA.
I have owned number of laptops with the LED light that shines down from the bezel. Several were IBM Thinkpads... and I also currently have an HP 2530. While those are much better then relying simply on the screen illumination... they are still vastly inferior to the backlit keyboards that I have used.
If I do not like the new MBA... I'll be giving it to my wife (who has been patiently waiting to inherit my existing MBA). Even though I am an proficient touch typist... I suspect that this will be a pretty big downgrade. I'll be willing to bet that the next upgrade will reintroduce a backlit keyboard... and I'll buy a new one then. Luckily for me... my wife is satisfied with my hand-me-downs... and she only uses computers while sitting at a desk in a well illuminated room.
/Jim
Please, report your experience next week! Maybe even PM if done so I know...