One more vote for HD here; the screen is out of this world. The size is perfect, and the sharpness is just unbelievable. Peering really closely at a printed page and the HD side by side, the HD wins out every time, unless the paper quality is super high. Then they're equal.
People make much of the "glossy" bezel and that it's a fingerprint magnet. That's not my experience. It is not glossy, it's just a finer matte than on the Glo. The Glo would also get marks on the bezel. The HD doesn't get more marks, but perhaps they look slightly different. To me, the fine-matte finish on the HD feels alot better, higher-rent, than the Glo. It feels sturdier too, like it's a harder, stronger plastic.
I'm gratified to hear that the internal card can be swapped out, but since that was how the power slider on my Glo broke, I am wary of trying. We'll see when I've filled up these extra 2 GB that I now have (if I ever do)
If I have one potential gripe, it is that the weight is noticeably higher. I like the extra heft personally, but I can see how somebody might object.
In short, to me, both the build quality and the screen quality of the HD _are_ the industry pinnacle right now. I really can't see any further meaningful advances within the current eInk paradigm. What I will want before I upgrade from Aura HD is some sort of merging of tablet and ereader screen technologies. I am curious to see what Amazon will do with Liquavista and their electrowetting displays.