I will say this about leasing, after weighing the options on the G8...
If you're going to lease a vehicle, it's better to lease one with a good history and a good resell value. On new models there is a higher residual because the manufacturer has no idea what the resell value of the car will be when the lease expires.
Essentially when you lease, the finance company is taking the risk that the car will still be worth a good amount when the lease is up. So you pay them to take this chance. On an established model with good history, you won't pay them as much.
On a brand new model, like the Pontiac G8, you'll pay a lot. Like $580/mo for a 3 year lease.
So for me, I think I'll keep my tC, which I'll own in two years. Between now and then I'll pick up a '68 Firebird, which would beat the pants off the G8 anyway.