After 40K miles, the OEM Goodyears finally gave way (I know, you're saying "what took me so long"). Replaced with Enkei PF01s and Michelin Pilot Super Sport 245/45R18s.
Stayed with 18" for performance reasons. Interesting that Pontiac called the 19"s the "Sport Package" when they don't put any more rubber on the road and increase unsprung weight/rotational inertia. Hmmm . . . . Form over function? That was one of Pontiac's weaknesses over the years.
Side by side of New vs. OEM. Interestingly, both wheels are Enkei-manufactured with "MAT" rims in 18x8 sizing, but the PF01 is about 10#'s lighter than the OEM:
OEM weight with completely worn Goodyears (52.2#s):
PF01 weight with brand new Michelins (43.4#s):
Glory shots of the G8 in its natural environment (at the pump):
Car is SMOOOOOOTH!!!! Sticks like glue. Wheelspin cut way down too.