The optional rear-facing third-row seat divides owners: some value it for kids and pay up for it, others call it a gimmick that only fits small children and costs you the spare-tire well. Cars so equipped shipped with only a compressor and fix-a-flat, and the seat can be removed to fit a full-size front wheel; retrofitting the seat reportedly costs around $2k.
Rear-facing third-row seat versus spare tire: useful or gimmick
Mercedes-Benz E55/E63 AMG (W211) · ownership