I have seen claims of dramatic increases in tool lifetime with post heat treat cryo, specifically in regards to drill bits. A friend of mine tried this however all he found was that it made them much easier to break. He just dipped them in a dewar of LN2 for the cryo. If you are going to try it, then for optimal performance you would want to do a post cryo temper to transform any martensite that has formed, as otherwise the steel will be in a highly stressed state. As well, cryo often leaves a region of the surface uneffected (have not seen the depth specified), so you won't see any benefit, even if it does induce one, until after the first full sharpening. This is something I have planned to look at, probably first with the Cold Steel Twistmaster.
-Cliff