If you want to know what muscles an exercise works, just think of where the tension has to run through. Deadlifts and their variations isometrically work your lats (keeping the weight close to your body and preventing your arms from getting ripped off) and both your traps and rhomboids (keeping the weight from ripping your shoulder blades off your body). Think about it, if you've got a big fucking weight in your hands, don't you think you'd need something to stabilize your arms? It's kind of like how your spinal erectors and abdominal muscles maintain your posture during squats or deadlifts. Stiff leg deadlifts are kind of like close grip benches in that they concentrate more on the hamstrings, forcing you to use a lower weight than vanilla deadlifts. As a result, your back isn't going to be worked as hard because less stress is being placed upon it.
That being said, if you really want to work your upper back do pull-ups and rows in addition to deadlifts.
i dont think that the stiff leg deadlifts or romanian, or whatever more bodybuilding version of the deadlift, is very good for the hamstrings. i only feel it in the junction of the hamstring and glute and only for a second.