I've loaded about 15,000 rounds on my two SDB's so far. The setup is relatively straight forward and if you take it slow, it's not hard to figure out even for a person new to reloading. You can always call Dillon and ask them about anything - they have excellent support and a unmatched warrantee, or post here.
The SDB can load approximately 300-500 rounds per hour, depending on your economy of motion and how many primer tubes you have pre-loaded. When I'm using good brass (basically anything without crimped primer pockets) and the machine is in good shape, it is very reliable. I tore down, cleaned, and rebuilt my .45 SDB in about an hour and a half, never having done it before, when it started getting finicky once. Of course, I was at least its second owner and it had over 60,000 rounds through it by then.
The auto-indexing feature of the SDB and 650 is a must-have, in my opinion. It eliminates the possibility double-charging the case, and there's less for the human operator to screw up.
To increase load rate to the range of 800-1000 per hour, get the XL650 and the automatic case-feeder. Then you leave your right-hand on the roller-handle and just place bullets on charged cases with your left hand.
If you want to load a few hundred pistol-caliber rounds per week, the SDB is a great choice. If you want to load more than that, or load rifle rounds, I suggest the 650.
-z