I believe the biggest thing we 3Ger's will have to contend with, is the smudging of the highly glossed finish.
Scratches? - Of course, if you take a key or any sharp object to any plastic, it will scratch.
Solution? - Buy a case 🙂
To answer the thread, I think the iPhone 3G will be as durable as it can be, taking into consideration the materials Apple have chose to manufacture it from. 😎
R-Fly