Lol, what's with all the trash talking people? The F5300 and H5000 are excellent sets with fantastic bang for the buck. If you are going to view either of them in a light controlled room, you basically overcome all their drawbacks. My 60F5300 calibrates beautifully (you can see the charts in my sig) and it easily hits 35ftL for dark room viewing with a max output of ~42ftL for bright room viewing. In daylight/bright room viewing, as others have pointed out, it certainly struggles a bit due to the lack of AR coating and lower peak luminance in comparison to the F8500. With that being said, it certainly doesn't make the TV unusable in daylight viewing as long as you don't have a bright light source opposite to the TV and behind the viewer. The F8500 is clearly superior in a well lit room and I don't think anyone is debating or arguing that point. The AR filter coupled with the higher peak luminance of the panel makes it the best "daytime" performing plasma panel made to date.
To ADU's original point, I think there is minimal to no advantage to an F8500 when it comes to picture quality in a dark room setting. The AR filter is unnecessary in such viewing situations and limits vertical viewing angles. Color accuracy and peak luminance are non-issues for both sets as they calibrate really well and can easily hit luminance range targets for dark room viewing. Both support 96Hz playback (CinemaSmooth) and the only real differentiator is that the F8500 supports motion interpolation, if you are one of the few folks who actually like it. This isn't an "attack" on the F8500, it's just stating that the cheaper sets are capable of achieving an equally magnificent picture and viewing experience in light controlled situations.
If you are sitting at around 7ft or closer, then the pentile subpixel layout becomes and issue due to SDE on the 60F5300, or the H5000 and the F8500 would definitely be the only set to consider for closer viewing distances.
Lastly, in a light controlled situation, the F5300B and H5000 actually have outstanding black levels and perform better than older F8500 sets, so they certainly aren't crappy/cheap plasmas that can't "cut it" when it comes to comparisons against the more expensive F8500.
Source: Zoyd's excellent work in compiling black level v/s APL
If I were the OP, I would much rather buy a 60 or 64" TV than a 51F8500. The jump from 51 -> 60 or 64 makes far more impact than having all the bells and whistles that come along with the F8500, especially when you plan on doing all your critical viewing in dark room settings. If, on the other hand, you can afford an equal sized F8500, then it's a no brainer to pick one up over the F5300B or H5000. If you do go with the F5300B or H5000, do make sure you check out the TV beforehand at a store at the viewing distance you plan to view at. If you are at exactly 7.5 ft, the SDE may be an issue depending on how good your vision is and how sensitive you are to it.