I think table image is the most important thing live, if you are a total rock you will be bullied left, right and centre.
If you are prepared to call the odd "daft" bet or make one you will pretty much be left alone.
I am also firmly in the camp of never showing my cards as a norm but if i were to go to a new casino where people don't know me i would certainly be showing the odd bluff etc. just to boost the "nutter" image

Moving allin blind is a good one for this too, just ask floppy!!!
I think the most valuable information is knowing the peeps you are up against this though comes from frequenting a place fairly often.
I agree, table image has far more significance.
Online, most players arn't paying attention unless they're involved in a pot.
Live, they've little else to do but watch, and so there's much more of the ol' he knows than I know that he knows palava going on.
Also a fair point about being familiar with the competition. Same faces again and again at the club, and so there's much more value in taking notes.