Jeff,
Corner weighting attempts to equal the weight distribution of the RF/LR with the LF/RR assuming the weight of the driver in the seat. If you are doing a high performance alignment (agressive negative camber, for example), it is usually a prerequisite to assure the characteristics remain constant for either direction during hard cornering.
If you're doing a full-tilt alignment with handling the ultimate goal, I don't think the incremental cost is out of line. For a guy that runs a few track events a year, is it going to shave a second a lap? I doubt it. I can't imagine there would be a benefit for the quarter, but this isn't my realm.
The good thing is you only need to do it once, assuming you use the same shop and that your car doesn't change too much between alignments.
Good luck,
Eric
01ACR