With a stock torque converter I wouldn't whole heartedly recommend locking it at WOT at the track. Ya, sure, I did it all the time, but I always wasted the clutch once every year. The stock converter and others with similar clutch designs just aren't designed for that kind of abuse.
As for performance gains/losses, well you won't see much if anything at all ET-wise. The big difference comes in the mph! Generally, with a stock converter, you could see between 1.5-2 mph increase when locking the converter. I always locked it very shortly after the 2-3 shift (and that's how I set it up in my race chip also).
As for a multi-disc converter that's designed for this type of abuse (like the vigillante that I'm now using), it's a little different story. You can lock them at WOT "till the cows come home" with no detrimental affects. I've tried two different ways, manually locking the switch before launch so it lock immediately on the 1-2 shift (that was a huge mistake!!) I don't recommend that method, the vigillante's because of their multi-disc design lock "very positively" and the combination of TC lock and simultaneous gear change is WAY TOO MUCH of an rpm drop, the car boggs badly.
So I went back to my old method of letting the chip do it within about 1.5 seconds after the 2-3 shift. This method works perfectly, and the engine won't drop down out of it's HP/Torgue curve.
With the multi disc design you should in most cases see a mph improvement in excess of 3mph and usually closer to 4 mph.
I'm a mph/power junky and could never go back to a non locking torque converter. There's a lot to be said about getting all or most of your horsepower to the rear wheels instead of eating it up as heat loose in the torque converter.
116.9mph time slips do wonders for the ego when on testing I leave it unlocked and run 113.
