Can't comment on the PenTile issue save to say that you shouldn't see a difference in image detail at normal viewing distances. Subtle things, perhaps...
Viewing distance is up to you, recommendations not withstanding. There are a few rules-of-thumb, based on this calculator
Pixel resolution threshold
This is the distance were a person with normal vision would just stop resolving individual pixels.When you combine individual pixels into a display, this becomes the "ideal" viewing distance in that your eye is able to see all the information on the screen, without seeing the screen.
THX wants you to sit where the screen is 26-36 degrees wide
SMTPE wants the screen to be no less than 30 degrees wide.
Too close: I can start to see the pixel array with normal corrected vision at about one screen diagonal on my plasma. I sit no closer than this, and call this my "excitement zone" when something has me on the edge of my seat, or better yet, jumping out of it. Note this is still ~2x minimum viewing distance based on human field of view...
Too far: lots of criteria, but a functional one is when you're sitting on the opposite wall. Sound quality is always bad along the walls, so give your head at least 2-3 feet of room behind it.