The material is more expensive to purchase and its harder to fix, I see an increase in selling cost and insurance rates.
These will be much more corrosion resistant too, a big plus in large chunks of the country where you're much more likely to lose a truck to the rusties than anything else.
This is a good question. Painted aluminum has long been in service on cars in the form of alloy wheels. While they are too thick to develop holes from corrosion, they certainly have a problem with the paint separating from the metal as corrosion spreads between the two. I've seen sufficiently deep pitting from that corrosion that I think it's possible aluminum sheet metal could see perforation in, say 10-20 years. There's also the problem that all non-aluminum metal fittings will have to be isolated from the aluminum or there will be bi-metal corrosion.