Ahhh Phil,
You do pass the occasional fur ball now don't you.
With that in mind, and since you pulled the grammar card, I'm thinking there are those who would quibble with (your sentence):
"It's not much use for writing intelligent posts with, that's for sure."
One ain't sposed to end a sentence with a preposition, and the "that's for sure" tag doesn't really absolve your use of "with" in the "It's not much use for writing intelligent posts with" which for all intents and purposes represents the end of the sentence (or independent clause).
Mr Churchill, in some sort of epiphany spit up the hairball:
"Up with this I will not put" pretty much flying the bird at this notion.
Normally one can easily correct the preposition ending thingy, but, I can't seem to move your "with".
"With it is not much use in writing intelligent posts" kinda blows.
And then there is:
"With (your brain) [there] is not much use in writing intelligent posts."
In which case "with" becomes entirely superfluous, we (or you) could just say:
"Your brain is not much use for writing intelligent posts."
But then intelligent becomes a bit worn, if we assume intelligent o be a brain thingy, perhaps just:
"Your brain is not much use for writing posts"
This finally invites your paperweight, assuming of course, that writing posts is a measure or brain value.
Hmmm.
The above content is my opinion.
