I wouldn't be worried. Apparently the issues continue in the 2017 models, but not everyone is effected.
I just got a 2017 MBP 13" Non TB and I was really worried about this. My laptop doesn't have any non functioning keys but it does have the problem that some keys (on the left side) like the "Q" key are louder (more click). I have found this to be the case when the computer is cool or hot. Now I am not too worried, since I can deal with a little extra noise, but I am more concerned about failing or malfunctioning keys
Why I wouldn't worry is that you still can return the computer. If the keyboard does malfunction you can send it for repair under warranty. If you do keep it I would invest the extra $500 you would have spent on a new model on Applecare.
However not to confuse your decision more but the 2017 models are showing nice performance bumps with Kaby Lake.
On a side note I was coming from a 2012 MBA and while I am still getting use to the keyboard I am starting to enjoy the clicking short travel. If you tend to really pound your keyboard it might feel like you are typing on concrete but if you are of a more light tap person, you will be able to glide through every input.