I think everybody is forgetting something here...
I would DEFINITELY take a new f8500 over a malfunctioning vt50. and really, those are your only choices.
when I bought my f8500, I had gone in with the explicit plan of buying a vt50. I unfortunately(or fortunately?) was about a week late, and could not find stock. shortly after that reviews on the new panny's came out, and it was clear that the vt60, and in some ways even the st60 were superior anyway. so I was going to wait for those. while I waited, salesman after salesman directed me towards the f8500. by the time the st60 arrived, the f8500 was the tv to beat. by the time the vt60's arrived, I preferred the the f8500 to the vt60.
I'm not sure what the deal is with color, until this thread I had not heard that calibrated color on the f8500 was an issue, and I have not experienced any issues with color reproduction on mine. color is not a sensitive topic of mine though. I can't think of a tv that had color that really bothered me.
the blacks on the f8500 are great, but do come with 'crt-like behaviour'. one thing that plasma is usually quite good at is holding black levels as APL increases. this is something that I never cared about, and I definitely enjoyed CRT's ability to get black with dark content more than plasma's ability to hold black with bright content. unfortunately it's not like the f8500 get's blacker with dark content though, it's more like 'about equal' with dark content and then rises to a significantly higher level with bright content. I would argue, this doesn't affect viewing pleasure though, as you simply can't tell blacks aren't black when the rest of the content is so bright. so it's a trade off I'm happy to make, if the other option is to have elevated blacks levels all the time.
so, all in all, you should be alright. focus on the fact you're getting a larger screen, a brighter picture, and similar blacks with great color and the most resistance to IR I've experienced on a plasma.
Displays: Samsung PN64F8500/JVC X35
AVR: Pioneer VSX-1018AH, 5.1 audio
Sources: HTPC(Mediabrowser), PS3, XBOX360, Wii, Sony DVP-CX995V
Control: Harmony One