IMHO
I am with Mark on this one. Any wheel built well, is stiff. I cannot tell the difference once I am on top and ridding.
Twisting spokes around each other does affect building. The tensioning of one spoke has a great effect of the tension of another, consequently when you try to put tension on to one part of the rim you add tension to another at the same time whether you want to or not. Also logic tells me that a bent spoke has an additional weak point, at the bend.
Trying and soldering does have some benefits. I believe that this is particular helpful in a wheel low a small number of spokes, say 24. Particularly in a "straight on" impact, say a track rider riding over another competitor. The wheel seems less likely to collapse completely. Bend yes, but stay rideable enough to get the rider off the track. This is a useful property when doing grass track racing as it is not unheard of for tracks to have "uneven" surfaces. Otherwise know as "****dy great big holes".
T&S does have a place on a "Classic Bike" as the bikes we call classics were often T&S, even if it was of little benefit.
Regards
Martin Coopland