Yes but there are other ways to indicate sleep mode (such as a watermark)
As for technical document readers, this is not exactly going to make people happy. I'll even venture to say that this problem makes using it undesirable for certain uses. The nature of documents that the DX is mainly designed to display can often require that they remain visible without refreshing often, which of course is what keeps the screensaver a bay.
So unless they fix this (bug), I'm afraid this wonderful piece of technology is somewhat crippled and I won't be able to use it as I would like.
I think this version of the software is ill-conceived for the DX where it appears to be just a port from the smaller Kindle with some added features.
the problem is, with such a huge company, it will take huge feedback before any modification will happen.
(best we start now)