Used to ride A Courier comp and an old Gary Fisher with steel forks back in the day, seem to remember it being pretty harsh though. So do Carbon forks offer much of marked improvement? Thinking lightweight Ti hardtail here.

i have some genisis io steel forks which are stiff and brutal, swapped them out for some exotic carbons and they do seem to dampen down the shocks/vibrations.

a smaller amount than people will have you believe. they do take the edge off though.

No idea about mountain bikes but it makes a massive difference on my road bike.

yea what thom said, i also have some steel pipedream forks which are slightly more forgiving than than the genesis forks
if your a bit of a pansy and your hands/arms ache after 10 mins its going to do the same with the carbons.

can ride mine all day, i prefer them in the winter as they are lighter, more forgiving on softer ground, maintenance free and have greater mud clearence than my sids.

Depends on the forks. I've ridden carbon forks which are quite stiff, and steel forks which are very forgiving. Pretty hard to make a blanket statement like 'carbon is flexible/forgiving/comfortable'.