Just got my Aura HD (espresso). It's my first Kobo device, and my second eInk reading device, my first being Kindle DX.
I borrowed a Kindle Paperwhite to compare it to.
My experience so far:
Screen: Amazing crispness/detail level when reading in daylight!
Frontlight: Works well. Compared to Kindle PW the lowest setting, 1 % on the Aura, seems to be similar to level 3 on the PW. (To me that's OK, because most of the time the lowest setting on the PW would be too low for me.)
The PW lights are slightly uneven at the bottom. That's better on the Aura, nice and smooth.
BUT: I would really like to have an "inverted mode", make the text white and the rest dark (like when upgrading etc.). @Kobo, Please make this!
Until I get this, I'm not sure I find frontlights much better than backlit iPhone retina. Time will tell -- and will surely test it ...
Also: Reading (k)ePubs in landscape would be nice, to my hand (not very small), landscape feels good.
The device feels and looks nice, but I'll probably find some case or thin adhesive material to make it less slippy.
The shape is nice, but the Kindle PW's more rubber-like material feels better.
Size: It's just slightly bigger than the PW, and not much heavier (if at all). The screen crispness is much better on the Aura, and the resolution is clearky visible. Both are nice and white, maybe the Kobo is even whiter.
The Kobo screen still is not big enough for my eyes to read PDF books (like O'Reilly tech books) without serious strain on my eyes.
Screen real estate:
It seems to waste some space at the bottom of the ePubs, as some have mentioned.
I will look into some of the tips mentioned elsewhere ...
Bottomline: I think I will be happy with the Aura HD. I did consider getting the PW, but after comparing, I think I'll prefer the Kobo.
(I like the fontweight option.)
Just my five cents ...