Millennium is cool...you can explain the whole lineup of discs in a couple of minutes.
Basically, the Orion LS (stable) and Orion LF (slightly overstable) are max D discs.
The Polaris LS (slightly understable), the JLS (slightly understable but faster and longer than the Polaris LS) and the EXP1 (overstable) are all fairway drivers.
The Aurora MS (stable) and Sentinel MF (overstable) are mid-range discs.
The Omega (stable) is the putter/approach mold.
Sirius (S) is the Millennium version of Star plastic.
Quantum (Q) is the Millennium version of Champion plastic.
Millennium (M) is the Millennium version of Pro plastic.
They also make the Omega in a supersoft plastic.