I received my MBP today, it's a refurbished unit in truly amazing condition. Very pleased with it. I do see the "grain" as it is being described. This phenomena can also be seen with widescreen DLP and LCD RP televisions as well. In the TV world it is referred to as SSE, or, Silk Screen Effect. At least with TVs, it is as a result of the low glare, high gain material the front screen is made of. It was unbearable with the DLP I purchased, and finally was driven to return it and spend quite a bit more on a plasma.
In the case of my MBP, although I can see it if I look for it, it's not a problem. Doesn't bother me at all. That said, considering what I went through exchanging three TVs before finding one without SSE, I can certainly sympathize with those who are bothered by it.
SSE is regularly discussed over on another forum I frequent called avsforum.com. Some are bothered by it, others don't see it or don't mind it.
MacBook Pro 2.0 GHz Core Duo 15.4 Mac OS X (10.4.8)