I've got a 5-way SuperSwitch in my Thinline Tele, which gives me, in addition to the 3 "regular" positons, both pickups in series (a "must have" for any guitar with 2 single coil pickups, IMHO), and both pickups in series out-of-phase; since they are in series, the volume drop is not as extreme as with both pickups in parallel out of phase; the tone is kinda nasal, almost no bass, a bit like playing through a half-cocked wah pedal; the tone also changes a bit with your picking dynamics (kind like when using an auto-wah or envelope filter); it's fun to use as a special effect, or as a nasal high-gain lead tone or for funky clan rhythm playing - but I'd say it's definitely NOT a must-have; if you've got the switch, and you have one more switching position left that you don't know what to do with, go for it; but it's not worth specifically modding a guitar for...