The full enclosure ones do exactly what they say on the tin - you can lop 90% of the noise off with something like this:
SilentDrive
and
Silentmaxx
The suspention method works reasonably well, but is not as comprehensive as it only cuts down on the case vibration, not the head (clicking) noises.
I have one of each of the picks above and they're both great - they both silence and cool - but bear in mind they are only rated to 10k and even then I'd be reluctant to put a Raptor in the Silent Drive.