I've got a '75 SVT and routinely use my SansAmp BDDI. I love the sound of my amp and am not using the pedal for tone enhancement or warming up (which the amp on its own really does not need), but instead use it to get different tones, as a volume boost, to drive the amp a little more and (most importantly for me) as an amp simulator when I only get a DI to the house PA (if the sound guy won't mic my cabinet) when using effects- especially distortion/fuzz and evelope filtering.
In the last case, I will usually run my effects into the SansAmp and send its parallel output (without tube emulation) into my head and the direct out (XLR- affected) to the house. Sound guys are usually much happier, and I get better tone reports when I do this, as opposed to just running an overdriven signal directly into a DI.
A large part of the SansAmps raison d' etre is to model tube amps ala the SVT, but I haven't found it redundant at all, and have been able to put many of the other features to good use.
-b