Oh crud Shazza I missed your post, I could have explained what you are seeing. Sadly it exists in the glossy version as well, primarily on the 15" MBPs I believe, the 17" I can't remember if they are effected.
Basically, Apple went with a cheap LCD on the MacBook Pros, and uses dithering to obtain their marketing claim of 'millions of colors'. There was a lawsuit filed, attempted(And failed I believe) to get class action status over this, and settled recently out of court.
Instead of using a true 24bit display(8 Bit per color) they went with a cheaper 18 bit (6-bit per color) display and are using software dithering to artifically enhance the colors.
That is what most people are seeing in recent when they describe a texture on their screen. It exists on all screen to my knowledge in the 15" MBP, glossy or matte, just the glossy seems to do a better job of hiding it. Rumor on it is that the glossy screen is a glossy coating over the regular anti-glare coating, but I don't believe that has ever been confirmed.
Sources for reading pleasure:http://arstechnica.com/journals/appl...k-pro-displayshttp://arstechnica.com/news.ars/post...-displays.html
A quick google will turn up much more, including one just recently filed in the same domain about the lower end iMac displays(Not the 24" but the smaller ones)
There is a reason I have external displays set up, though I am not as picky as maxrule is I don't believe. I don't make money off my photography and mine all stays digital for website design and similar, so I am not as strongly affected by it, due to the fact that many displays fall under the same problem.