Source: PlanetHalfLife

[UPDATE]
PlanetHalfLife just reported that they have received another e-mail from Erik Johnson informing them that it might take another day for the fix to be released:

We're still working through some testing on this release. It might be something we'll want to hold for another day and release tomorrow.

[/UPDATE]

PlanetHalfLife got a confirmation from Erik Johnson, that Valve is planning on releasing the Stuttering Fix for Half-Life 2 today:

That's what we're shooting for.

So if all goes well, then we will have more on this soon.