I can see clearly now the fog has gone

I noticed that even after I increased my draw distance to 256 I still couldn't see very far, although I could see the silou...silhou....outlines of things some way in the distance. Now knowing a bit about 3d graphics I figure there's no easy way to do that any faster than just drawing the objects properly. Immediately I think of fog, so I investigate prefs and raise the "fog distance ratio" from 1.2 to 2 and instantly I can see everything! Like for miles I can see stuff that my PC was rendering all along but was then obliterating with grey.

The main reason to use fog in a 3d engine is to reduce the effect of 'popup' where stuff just appears suddenly as it comes within the draw distance. This is kindof irrelevant in SL as stuff 'just appears' all the time due to the way content is downloaded. There is another reason to use fog and that is that it creates a better sense of depth to the image. With the fog setting at 2 there wasn't much depth perception so after a bit of experimentation I've settled on 1.6 as the ideal setting. I think LL should consider changing the default to 1.6. Going from 1.2 to 1.6 is like having cataracts removed.

They must also consider that there are people with a computer that just barely runs it, like mine.

Maybe you should start a donation program where everyone donates Lindens to you, you convert it to $$ at GOM, and then you upgrade your system.

The fog ratio doesn't make any difference to performance. In general anyway- SL could do random performace dependant things based on the setting - it's usually a fixed cost operation. Draw distance is what affects frame rate (although it makes surprisingly little difference on my PC).