A couple things to consider:
1) What are YOU planning on using it for? If you just need an ereader, then the Glowlight more than fits your needs. If you want access to full color offerings like magazines and other multimedia (web, games, video, etc), then you will be happier with a tablet.
2) Will you use the device outside A LOT? Tablet devices, including the HD models can be read outside with a little work (brightness, background colors, sitting in shade) but the eInk screens are FAR superior in sunlight.
3) Do your eyes get tired reading LCD screens? Mine do not, but yours may tire. eInk is just like reading a prined page, tablets are like reading a computer screen.
Basically it's up to YOU. I chose device versatility with the Nook HD, but others prefer the focused reading experience of the eInk readers.
I've got an HD, which I use mainly as a tablet rather than an e-reader. I do most of my reading just before falling asleep, and I'm one of those folks who find an LCD display to have a caffeine-like effect. If I use the HD, I'll stay awake for a couple of hours, sometimes more. So instead I use my old NOOK 1e with a clip-on light, and after a chapter or two it's time to put the NOOK away and get some sleep.
OK....it appears to be a moot point insofar as my trading up or laterally, depending on how you look at it. I went to the store and they told me an upgrade (which I got), has to e to a "like device." I couldn't upgrade from a reader to a tablet.
I think I'm OK with this decision being made for me. I'll probably wind up going for a Nexus 7 or 10.
Thanks to all for your input.
I've had the new Nook Glo for about two weeks now. Before that I did a lot of my reading on my Nook HD. I've already noticed that I'm sleeping much better reading on the glo. I recently read a library book on the HD, and found I had trouble getting to sleep again. Finished the library book and went back to the glo, no trouble falling asleep again.
and the battery life on the glo is so much better.
For a reader, the combination are a real advantage on a long trip, since recharging the HD on a long trip can be a pain, so sticking to the eInk device while reading and restricting the HD to the other functions can substantially extend the effective battery life of the HD.
I have a glow light and a 7 inch HD+ tablet, and there are pros and cons with both. What's great is that I have the same library on both.
The tablet is good for web surfing, and I can easily read some new sites with it, along with books, but I cannot read it easily outside. Also, with its cover on, it's a bit heavy for reading in bed. I also have to charge it a couple of times a week.
The glow light unit is extremely light and is wonderful when reading in bed. It also works well outside, and the biggest plus - I can use it for hours and hours and it still has a decent charge. It's just below 50% now, and the last time I charged it was on Christmas.
For taking out library books via Overdrive, the tablet is far superior because books can be downloaded via wifi, but it just takes a couple more steps to do it with the glow light (same process I used with my Nook 1st edition).
Buying books is easy with both units.
If all you want to do is read books, then I'd recommend the glow light unit.