Well I for one am IN. Seems to be a lot of Thread Crapping on this one, but I look at it this way:
I get a 5% rebate on my current Credit Card for Purchasing Gas, and use that anyway
Now I will get 5c a gallon on top of that
Where I live (Southern CA) Mobil is the cheapest anyway (and offers a cheap carwash to boot). I always thought Mobil was one of the cheaper ones (next to Arco, that is) anyway. Not like Chevron.
I already USE mobil to fill up, so I have nothing to lose, and $20 to gain...
The ONLY negative I see on this is the 90 days and the $20 limit. Wish it was forever.