erm...
bouncy, swaying when on uneven road, skipping mid corner, etc
but mainly it depends on the driver (the feeling especially when compared to new), but i know that this cannot be done

if it is hard it does not mean it is still working fine
it depends on the spring rate (hard spring rate tend to give false impression that its still in good condition)

if in doubt, try doing compression test at the shop u intend to do revalving. i belive that they can determine f its still in good condition.

what car u driving btw?