Last I used a droid with shields they work but only as an extra layer of HP for the droid. I'm not sure if that's the final intended implementation of them. I'd assume not because (at that time at least) the shields didn't regenerate if they got destroyed.
They should regenerate at the 2%/hour figure mentioned on the rules for repair. That page will be rewritten for the new repair release (which is nearly ready!) but the 2%/hour amount will remain.
"On two occasions I have been asked,—"Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?" I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question."
- Charles Babbage