Picked it up from Lowes, on sale for $2.50 for a 4 pack. Wanted to share my experience with you all...
EXCELLENT for cleaning my FX's willow interior. All the vinyl pieces have black marks on them from people stepping on when getting in/out of the car. 3-4 passes with the magic eraser and they are all gone! Another thread said that they work well on the speaker covers also but I have not tried it out there yet. Additionally my willow seats were a bit dirty from lugging tires around without laying down any protection. The magic eraser took out all the marks left from the tires too.
I tested it a bit on the driver's seat and it seems to work well. Not sure if it is safe for leather though. In the pic below, the area circled in red was cleaned with the eraser. Can anyone chime in on this area?

Hope this helps!