Hopefully Giovanni Cristi will reply to this, as he is quite familiar with this subject. Giovanni, ya out there??

Yes Chuck, I'm here.
Back in 2003 I conducted a research here at Mackenzie University to verify the effectiveness of Vibratory Stress Relief (VSR) of welds.
The research was carried on two different pieces of 4 in, carbon steel pipes, and demonstrated that VSR actually removes the residual stresses in weldments.
The results of the research were used to prepare a paper that was presented before the Brazilian Welding Conference held in 2004.
A copy of the paper translated into English is available free of charge from Mr. Chris Fischer at:  formula62@AOL.com
A word of warning: although VSR is actually effective in removing residual stresses from weldments, it is not yet accepted by American construction standards, such as ASME VIII for pressure vessels and ASME B.31 for piping. In those cases, thermal stress relief (TSR) is still mandatory.
VSR requires less time and less energy consumption that TSR, but its main advantage is that it doesn't produce any warping, as TSR does.
Example: paper making machines, also called Beloit machines from the name of the first constructor, are heavy and long horizontal machines that not rarely reach 300 ft in length. They are supported on a structural steel frame that must be erected and levelled following awful strict tolerances.
Well, as I've personally observed, Beloit machine manufacturers prefer to use VSR instead of TSR to treat the structural supports after they've been erected and welded. Why? Because TSR would take them out the tolerances and VSR does not.
Nothing wrong in this procedure. The structural frames of the Beloit machines make integral part of the machine itself and do not necessarily follow AWS D.1, which has been thought for civil construction (bridges, buildings etc.)
Let me know if Mr. Fischer has sent you the English version of the paper.
Giovanni S. Crisi
Sao Paulo - Brazil