I really dig the 3rd channel, but am recording 4 or more total and mixing later. Gives a lot of flexibility and ability to tweak things, not just firming up the center, but also the bottom end, and some control over direct / reverberant pickup which can be really nice.
I'm doing it either with 3 or 4 omnis, all in a row across the stage-lip, or spaced like a Decca tree or closer than that and baffled.. or two cardioids and a center omni.. or sometimes unusual setups for what we are doing like OCT (optimum cardioid triange, which uses two side facing supercards and a center cardioid). Getting the perfect mix live would be less optimal since fine tuning the balance is a big key to the flexibility, but like TS, people used to do that a lot. Think of all those old Nak 3>2 channel boxes.