I've been considering the HDX. I had the original Kindle Fire, and I have the HD now. I love the hardware (played with it in Best Buy) and some of the improvements to the OS, such as hiding the carousel. And at first I was all "I want it". But I've reconsidered.
1. Wifi usage.
I don't read on my HD. I read on my Kindle Keyboard ereader. Yet the Kindle app on the HD, this month, has been continually "syncing". I've never downloaded any books to this device. I suppose it keeps info about my library on the HD but I wish it wouldn't. I've shut off every option having to do with whispersync, auto update, etc but nothing helps. I'm on limited bandwidth, 5G/month, and this month is the 4th time this year that the Kindle HD will put me over my bandwidth limit and cost me money, this month it's the kindle app using up 1.6 G in 10 days, 3 other times it was updates that came at the end of my cycle - and no option to NOT get them until I was on free wifi.
My Nexus 7 2013, on the other hand, behaves itself and never loads anything I haven't asked it to, once I set the no-sync and no-auto-update options. I can go into wifi setup and designate my hotspot as a paid connection, and then it doesn't ever use it without my permission, even for things that DO auto-update. Love that feature.
2. Games.
That's what I do on my HD. Play games and surf the web. And the games in the Amazon store are always behind on updates. And yes, I know it's because Amazon reviews the updates before posting them, but it's just unacceptable. For example TODAY I got the Amazon update to my town building game for Halloween. All the quests are due by Halloween (today) so I can't even play them. On my Nexus 7 2013, the same game, I got the update 6 weeks ago. I've seen them lag by 3 months.
Thing is, I can't see that either of those issues have been fixed on the HDX. And they spoil my fun, much as I like the device itself.
I've also got my eye on a Samsung 8" tablet. Love even holding that thing. But the price is steep...