Should rotors have no rub at all? I just installed a new front disk brake and the rotor rubs a bit once per rotation.  If I take the rotor off and place it on flat surface, it seems totally flat but once installed I can see/hear it rubbing onto the installed disk brake caliper once a rotation.  It's enough friction that it's making the wheel stop spinning pretty soon compared with when spin it with the brake off(not sure how to quantify it)

Is this normal?

(The new brake is an hydrolic Avid 7 Elixer and it replaced the original (also hydrolic) Avid 7 Juicy that came with the bike.  It's the original rotor.  The fork is a Lefty and therefore there's not any adjustment to be done on the wheel.)
Some rub is OK. No rub is optimal. Normal riding can bend the rotors, so the "no rub" situation never lasts forever. This can be fixed though.

You can adjust the caliper to reduce rub (or completelly eliminate it). The bolt holes are not very tight so you can play around with offseting the caliper accordingly. Just unscrew the 2 allen bolts a bit and start playing around with offsets. Looking through the brake pads and disk to a bright coloured floor (e.g white) makes this process very easy.

If the space of the pads is not enough to allow zero rub then you can try to straighten the disk. Use a clean rug/paper towler to grab it and give it slight push or pull on the spot it's bent. Never touch the rotor with your hand because the hand has a bit of oil which can reduce the performance of your brake.

The fact that your brake is new doesn't mean that it should be 100% rub free. There is a small possibility that the hub 6 bolt platform is slightly off. So a new disk will always look bent when rotating between the pads.