S30V is a knife steel that Crucible came up with specifically for the knife market. It's strengths are that it holds an edge for a long time and it has good corrosion resistance.

Its weakness (according to many usage reports on a variety of forums) is that it chips fairly easily when stressed.

I only have one knife with S30V steel (which has not been used hard) so I can't offer any personal data points.

When one gets past the knife steel flavors of the month, I find it interesting that many of the top makers who build knives to be used still prefer D2 and other good carbon and tool steels.