From what i noticed the hard way (yesterday i got a G751JY), even though this laptop is a beast.. there are some damn serious matters (both hardware & software wise).
Problems:
SOUND
Well sound is pretty terrible. *I am a technisian in a computer service department and comparing all laptops i have tested so far, i believe this laptop's sound system is way below average. Speakers are producing vibrations and i guess you have already noticed the FRUSTRATION!! (on 70% volume all i hear is brBrbRBBRBRbbrbrrbrBbrbrBRR..)
(by the way most vibrations are coming from the mouspad's buttons (and in my case mostly the left one because it is more loose...) Just give pressure on those and you will notice vibz will disappear. If you put a bit paper under gaps maybe you have a hillbilly fix)
headphones also sound is so freakin mat and you do not have to be an audiophile to notice that (you simply cannot listen with headphones, without the asus audio app first installed, which ofcourse is trying to apply a ton of freq handling and effects on the sound)
So the core problem here may not be the speaker itself, but bad quality of components installed in laptop (such as mousepad buttons and others).
BOOT
I haven't seen such a buggy boot before.
Possible symptoms:
BOOT is hanged after power on. (It could have shown logo - it could have not.)
Double small split screen on boot after restart
Restart hangs (if you are unlucky and this is a windows update restart - you could say goodbye to windows if you dont have recover disks) - (possible fix is through bios to disable quick boot)
After restart screen cannot get many times powered on again. (and this is I'm afraid not the same problem as above) so here we might have 2 boot problems
KEYBOARD
My left shift button needs a hammer so that it gets activated.
This is a big disappointment for me because... most used laptops I have fixed at work (coming with a problem on keyboard or mouse) have the problem located on either left shift or space buttons. So this is not a good sign for my "brand new" laptop (just remember above I mentioned that I got a loose left mouse button so I hope I did not get a refurbished laptop)
other than that, laptop rocks (but I am still about to return it for a new one, which will 90% do the same exact things). BTW if i get again a not working laptop, I will demand a compensation. This is a buisness laptop ffs.