Nah should be fine... Cards are made to operate at those temps and have a built-in security that shuts the card down if it gets in the danger zone. Lower temps are always better though 
Think danger zone is above 120-130 C
Think danger zone is above 120-130 C
I disagree with this advice.
Check this thread for additional opinions:
http://forum.bitcoin.org/index.php?topic=18229.0
My 5830s are running ~60* C (open case with a household fan moving air through the case 24x7.
Why do you disagree? Just because others keep them lower? I stated that lower is always better, but the fact of the matter is: It is still safe to run your GPU @ 90 C.
I like to keep mine below 80 C. Your disagreement does not make any sense, since you do not state any reasons. GPUs are made to run hot... Better to keep them cool though.