The Kobo Aura HD is definitely the best of the Kobo readers, the build quality of it seems pretty good, it's the newer Kobo Aura (the standard 6") that has a lot more issues. For me, it's always concerns about firmware/bugs that matter with Kobo. However, if I was in the market for a bigger screen, the Aura HD looks good. Also, it's the only real option that is available, unless you are willing to wait and see.... and who knows how long that wait could be.
For non-registration, the Pocketbook is probably the best option, but from video reviews, the light on it isn't that great when compared with the new Paperwhite (and both the Aura's). If you are willing to root, there are always options in the Kindle Developers Forum to root and disable the need for registration, no idea if they are sorted for the new PW or not though....
You can apparently get T3's without the cover, but so far there's only been any mention of that in Germany (
source).