Note, the sony flat rate repair deal that I mentioned above is not a warranty/etc. It's basically an arrangement provided by Sony to anybody with a d7 or d8 or d100 (but not an M1 since it's not a consumer deck) that provides whatever repairs are necessary for a fixed price, including head replacement, etc.
Thus, a very real advantage to a d7 or d8 over a d3 is that with a d7/d8 sony will, for a little over $100, rebuild your deck to working condition (as long as it wasn't abused).