I started with a SDB and have been very happy with it for about 10 years. Only a few minor problems that most have noted here. The only real interesting problem was a timing problem between the shell late and the primer ram. The shell plate would hang up on the edge of the primer cup. Tried the adjustment,,,still NG. Called Dillon, explained problem, they said the shaft on the primer ran was BENT!!!
and replaced it.
Went on to buy a used 650.
The 650 is just for 40 and the SDB is used for everything else (4 other calibers).
Both presses are great but each has its peculiarities!