It wasn't until I had a slow news day today that I really got a chance to try the Cloud Reader. So it wasn't until this morning that I noticed it's missing a basic ability I expect in apps. Never mind the limited annotation or missing audio/video support (I bet they're coming); I just want some basic things like the app running in the background.
I cannot queue up my ebooks to be downloaded, and that's a problem. I have hundreds of Kindle ebooks and I don't want to have to download them 1 at a time. That's a waste of my time. Right now I'm bypassing the problem by sending the ebooks to the cloud app from the Amazon website, and this does work. But if I'm going to be stuck with leaving the KCR to manage my library then why not just go back to the native app? It shares the same inconvenience but it has all those extra features that the KCR lacks.
The app is also noticeably slower than the native Kindle app. It takes longer to load as well as longer to open a book. And it also takes longer to open the Kindle store than if I visit it natively in the browser.
Web content was never designed to be natively installed on your local device and the Cloud Reader is proof of that. If you're going to make a faux app based in HTML5, it needs to act like an app. If you can't accomplish that then don't make it with faux app.