Reply #2: In my own opinion that would depend on their design/intelligence

[Posteritatis]

For purposes of the discussion I'm assuming that the robots are doing ethical things in the course of their service - not engaging in crime, being used in combat - and that they're not being treated primarily as disposable. Any of those would heighten my ethical objections independently of the robots' intelligence, assuming there was any intelligence at all as opposed to, say, what a typical car or laptop has now.

Something smart enough to discuss novels with me capably, or genuinely emote? I'd never feel comfortable with something like that being designed to serve. If it wasn't that intelligent but had the outward appearance of it for form's sake (assuming for the sake of discussion that we can spot a difference, e.g. a non-intelligent robot that is programmed to speak well and politely), it would be another matter, though I'd probably prefer it be clear that it wasn't intelligent enough for me to want to classify it as a slave.

If it had the intelligence of, say, an African grey or a particularly bright dog or something, and was designed as a service robot? That'd be something else.

For a gray area, I wonder what I'd think of a highly intelligent robot which was not only designed to serve, but designed to feel joy and fulfilment in the task while being aware of that design? Would it be ethical to design such a being? If so, would it be ethical for me to want them "freed" from that design, assuming they got a form of happiness from said design and weren't being harmed? I don't know.

I actually read a short story recently about a robot which spent time in all three of those states; it's "Zima Blue" by Alastair Reynolds, the last story in a short story collection by the same name. I heartily recommend it, and anything else by the author.