Even Adams admitted, in his last couple years, that this technique no
longer works with "modern" films (whatever that means).  You can get
pretty much the same effect, however, by diluting the developer and
reducing agitation frequency in conventional development; I've seen a
difference that looked about like a one stop pull just by reducing
agitation from once a minute to once every five minutes in HC-110 G --
except that the shadow detail was about the same in both (because
shadows don't locally exhaust the diluted developer as highlights do).
I've never seen streaking (aka bromide drag) with HC-110, though some
have reported problems with reduced agitation causing this with other
developers, especially with faster films that contain more bromide to
begin with.

Do be sure to use enough active developer -- with HC-110, at least 3 ml
of syrup per 80 square inches of film (135-36 or 120 roll), at least 100
ml of stock solution for D-76 or XTOL -- even if that means you develop
a single roll in a double tank (use an empty reel for a spacer).

You can pick up 1/3 to a full stop of real shadow speed with this
technique, depending on the film and developer, by extending development
to recover the contrast level you'd have had with normal agitation at
your original time -- what you're doing, essentially, is developing the
shadows more (maybe a lot more), but not adding much to the highlights.
 No, it won't bring up details that weren't there to begin with, but it
does wonders for the rendition of stuff that would otherwise be too
faint to see readily in a print or scan, and you get the extra speed
without the contrast increase of a push.  Takes longer, of course...