I rather like mine. I have the Mini for pocket ability, but the HD screen (and faster CPU) of the aura makes manga readable without converting it ahead of time - and the extra inch over the Glo means I can fit more text on the screen.
The big downside is the slippery back - even with the angled back, it's hard to hold on to one-handed, so reading is a two-handed affair, like with a larger hardcover. If it was the grippier back of the Glo or the Touch, it'd have been much better.
If you need the SD card slot or graphics, it's worth it over the Glo or Mini. For one-handed use, the smaller screen of the Mini isn't a hindrance if true only reading ePub files.