Have you tried the various OLED (AMOLED, SAMOLED etc.) devices? When showing black they are effectively off, so white (or green or gray) on black text is relatively soothing.
My main reading use case is in bed at night. I have a little booklight for reading actual paper books, but I think I'm waiting for an AMOLED 8" tablet for e-book reading. It works pretty darn well for my phone in low light conditions. (In fact the main competition for an 8" tablet would be one of those giant 5" phones with AMOLED).
Sometimes, OLED screens are even worse than your average LCD. For example, the Galaxy S has beautiful colors and the bright of a thousand suns, but it's awful for simple white-on-black text. The glyphs are very irregular and have jaggies. I think it's because of the PenTile arrangement of the pixels: http://pentileblog.com/wp-content/uploads/2011/05/pentile-sh...
I have an OLED device, with probably the cheapest version of this technology available, it's using pentile, and I haven't noticed the issue with white text on black though it is occasionally noticeable (though never annoying) to me in other contexts. My device does have a small screen and therefore a relatively high pixel density though. Until the jump to Super AMOLED HD a lot of phones seemed to be putting the same pixel density (and pentile arrangement) on phones with screens an inch bigger e.g. my device is 266ppi vs 233ppi for the Galaxy S.
People seem to get a bit religious about pentile. It doesn't make any sense to dismiss (or accept) it without considering all the other parameters. It's designed to make it easier and cheaper to hit certain resolutions and densities. If I could get more pixels or density for the same money then I'd happily take pentile. If there's not much extra gain over not using it, or not much extra cost, then I'd happily leave it out. It also, for whatever technical reason, seems mostly to be associated with OLED technologies, though OLED does not necessarily imply pentile. I think Samsung brands their non-pentile AMOLEDs as SAMOLED plus and they have them either on the market or due very soon in both big phone, massive phone and mid-size tablet varieties.
However, OLED does have the one advantage I mentioned about reading in the dark which decides this for me. For that reason alone I personally am waiting for a sufficiently high-density AMOLED tablet for reading purposes. Pentile will be just one factor in weighing up my options, certainly not a deal breaker.
My main reading use case is in bed at night. I have a little booklight for reading actual paper books, but I think I'm waiting for an AMOLED 8" tablet for e-book reading. It works pretty darn well for my phone in low light conditions. (In fact the main competition for an 8" tablet would be one of those giant 5" phones with AMOLED).