An owner's opinion (after 3 months)
The author of this article is correct about the interface, it is bad. Really bad!
I have gotten somewhat adjusted to it's limitations after a while so that it is not quite as bad as when you first begin using the device; I guess I've just stopped trying to use the device for certain task to avoid the user inferface weaknesses.
I think the current UI is fundamentally broken, I don't think it can be "fixed". I think it would be best to completely redesign it from scratch. There is no feature of the current UI that I like. I hope an upcoming firmware release will introduce a replacement interface, but I have not heard any news that iRex is planning that.
An example of a limitation that I find completely maddenning is it's inability to easily jump to some arbitrary page number. This makes it impractical to make use of an SD card loaded with a bunch of technical reference manuals. My most common usage is not supported by the UI: I would want to open a book and go immediately to the index. even if I've never opened the book before within the reader. I might moveup and down a page or two to find the topic I'm looking for, and then jump to some arbitrary page. I have found this series of tasks so frustrating and impractical to complete that I have not even attempted my 2nd most common book task: going back to the index, and then jumping to a different arbitrary page if the first one didn't contain what I was looking for.
The hardware is great, the rendered pages are very easy to read, and I think all my complaints (I have more that are unmentioned) could be solved in firmware.
The device is really good for reading materials where you start at page one and continue forward one page at time. For now I am only loading it with materials that I intend to read that way.
The device would be killer if it could be made to behave more like a real book. It won't come close until it becomes easier to jump to an arbitrary page number.