1. How tall were they? Stereotypical/ actually physically impressive. I thought of them as more or less human-sized, if a little larger, even. Just larger and very burly. Dunno why, just sick of them being these little ankle-biters.
2. How strong/powerful/agile/fast were they? Despite having all of this amazing technology doing everything for them, I see them as being surprisingly strong. Perhaps not overly fast. And not exactly leaping off of walls Yoda style
3. How did they sound? (Speech) This is purely personal preference and imagination I think, but I always pictured them as having a magnificently calm yet terrifying and powerful voice with authority and cruelty. Like this -> http://www.youtube.com/watch?v=iigqd3yxaVI