^^based on this, you should run far far away from plasmas, haha.
the reason to buy a plasma is picture quality. if you're not looking for the best picture quality, there's no reason for plasma.
but fyi, the green dots is called dithering, it's the way plasma works, all plasmas. they are not made to be computer monitors, you are not supposed to sit 2-3feet away from them, and if you don't, then the dithering is no longer visible.
the lag on the f5300 is about average compared to current flat panels(including lcd). if the f5300 was 'unplayable' I would suggest lag being your primary focus. the number of choices you'll have with under 30ms of lag will be fairly small, and it'll save you a lot of returns to buy from that list only.
I'm not entirely sure what you mean when you say refresh rate, but most TV's these days have the frame interpolation stuff that gives the SOE. I guess really cheap '60hz' lcd's won't, but otherwise it's pretty common nowadays.
you should calibrate(at least a diy job) before judging a tv. the f5300 has been calibrated to reference quality colors. if your monitor is that much different, either the f5300 was not doing what it's capable of, or you don't want reference color.
nevertheless, the key here is you are using this as a computer monitor, and that is one task a plasma should never be used for. I mean, I have my htpc hooked up to my tv, and I use my plasma to surf the web and such, but I do that from my couch 10 feet away. a plasma as a dedicated computer monitor sitting on the desk 2 feet from your face will always be worse.