Princeps of Deceit doesn't let you move outside your deployment zone, so it isn't really like scout in that regard. In general I've found it isn't reliable enough to provide a significant benefit. You can't really risk leaving a unit in a position to confuse the enemy and then guarantee you can move it to where you want to afterwards. I've found it a gimmick for the most part.
Of them all, Strategic Genius is probably the most useful. Being able to re-roll reserves, either successful or failed, is pretty key. Conqueror of Cities is pretty cool, too, but it's obviously terrain dependent.
In all cases, I've yet to find the Warlord traits to be very useful one way or the other. This is the generic list, though; I'll be very interested to see what specific warlord traits the Tau get when they (finally) get a new book. The ones Chaos got are actually fairly cool.