We have got DS (4) the Kurio 7 for Christmas (mainly on Tesco points!) and so I've been having a play this week. I am very happy with the pre-loaded stuff, but I also wanted to see what was available beyond that before I lose hours of my life on fruit ninja and World of Goo.
So far, I have downloaded the Kindle app and a Harry (Bucketful of Dinosaurs) book as a present for DS (although it does come with a reader, I thought the children's book shop in Kindle was better), the Audible app (for audio books - things like Winnie the Pooh read by Stephen Fry and others) and I've bought a track from Peter and the Wolf (music & words) in Amazon cloud player as a tester. The sound from the player itself is great for games, but tinny when it comes to playing the Amazon stuff - until you add speakers (just little computer ones), and then it's FAB.
The camera is fine, although the picture quality is a bit meh, but it'll be loads of fun for DS. I prefer to use my camera to take pics anyway.
And I can get mumsnet on it, no problem! Some of the complaints in the reviews have been about what you can access through safe search, but I accessed the sites I wanted (e.g. I tested cartoon network for the games) through the Android interface, not the Kurio one, so I'm happy.
Other reviewers have said that their children might as well play on their phones. I didn't find that comment at all helpful. I have a BlackBerry and will NEVER let DS use it (plus, it doesn't have anything fun on it at all). But, each to their own.
I do agree that the screen can seem to "stick" a little at times, but it's probably because 1) I've kept the protective screen on and 2) I'm crap at touch-screen stuff (even on an iPad, for goodness' sake). It does say in the manual that responsiveness will vary from person to person, and I am getting better at it, so I think it's probably my fault, rather than the tablet's.
All-in-all, I think we've made the right choice for us (it is the only tablet in the house).