Having now had four GM vehicles with head up displays (sic) I'm very surprised to find that the '05 STS we just got has the HUD lens polarized exactly out of phase with normal polarized sunglasses. It literally is completely gone when wearing sunglasses, which indicates they put the lens at 90 degrees off from where it should be.
We had absolutely no problem seeing the HUD with polarized sunglasses in our '92 Bonneville, '00 Grand Prix and '05 Corvette.
If you tilt your head to the side, the HUD gradually reappears until your head is completely sideways and then it's at full brightness.
BTW, the navigation screen is polarized correctly. I can read it perfectly with sunglasses on. The climate control is a little off, it looks deformed through polarized sunglasses, but it's still readable.
Anyone else notice this with the HUD? I'm going to mention it to the dealer at the next visit. Perhaps there is a fix? Change the plastic HUD unit cover to one polarized differently?