I have the Amazon cover, and it is really nice. I have the special offers. I do have to tap the screen to get to my screen after I open it. That doesn't bother me. What I like even better is I can shut the cover and know that it's going right to sleep. Other touch readers that I have, if I close the cover without turning it off first, it will do things like change the page etc. So to me the closing ability is even better than the opening ability.
There may be some covers that can do the same thing. I have even heard of people attaching small magnets to non-Amazon covers, slipping them inside covers, etc, and the same thing working. Haven't tried it myself.
I should clarify my earlier post. My only 3G Kindle is a keyboard model, not the Paperwhite. Perhaps someone with a paperwhite can test the downloading of archived pdocs over the 3G and report the results here.