I too am interested in the 7 but I had asked about it at my williams sonoma and the person told me that it is still gear driven and not a worm drive but it has much more power, which i knew. He also said the bowls from my old 5 would fit but after talking longer I'm not sure how much he "really" knew.
As for my 5qt, it has to be atleast 15 yrs old, gets used atleast once a week, and I have not had it serviced, atleast not yet (probably just jinxed myself!)
tom