Mesh keyframe option in 2.42a

When you press ctrl+I in Blender 2.42a, there’s a new option for “mesh.” What is this and how does it work?

Nothing happens with Ctrl-I. Just I-Key will give you an option to “Mesh” that’s always been there; it used to set Relative Vertex Keys and now (on Meshes) sets Shapes.

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It creates a shape key. I don’t know if there’s any other reason to use it other than as a quick way to make a shape key while you’re modeling.

<edit>

Oops. Fligh’s right of course that it is I key only, not ctrl-I… (For me it’s actually fn-I… but that’s another story…)

Oh, yeah… i knew that. I meant when you press Ikey. Sorry.
So it can’t actually be used to animate the mesh?
For example, say I wanted a part of a mesh to extrude itself over 30 frames or so. The solution I’m using now is a Boolean modifier, and it’s working fine.