My experience with Amazon's own apps (such as FreeTime) is that they're not using the best developers and designers. Frankly, this doesn't surprise me. I'm a big Amazon fan but they're not the best software developers around; that's not their business. Amazingly it took the Amazon development "team" nearly a week to fix a bug in the reviews of the Kindle Fire HD that prevented anyone from reviewing the product. And the VERY annoying "zombie carousel item" bug that's been there from day one still isn't fixed on the KFHD.
Add to that the fact that the Amazon business model is simply NOT devoted to providing the best possible support for non-Amazon content and you get what you get.
Having said that, however, I'm more impressed with "FreeTime" than some others here. Although it's being marketed as a form of "parental control" it's actually more flexible than that.
For example, my wife and I can now separate our individual content items, (i.e. books, videos, apps), on the KFHD. I have no interest in limiting the time she spends reading her books or playing her games but I can now find my books without having to sift through her immense library.
Furthermore, the underlying "user profiles" can be twisted into the "Collections" feature that so many people complain about being missing on the Kindle Fires. Set up a "user" called "Mysteries," for example, and provide access to selected books in that category. Admittedly it's a little odd to give "Mysteries" a gender and a birthday but at least I can set up a content category that includes both books and videos (purchased from Amazon.) Of course, a true "tagging" feature for items would be better but as noted above, I've given up on Amazon being a true "software" company. They sell stuff. All else is a secondary priority.