(Referring to T20)
The main problem is that computers are dumb. Getting towards something able to replicate a human intellect requires an enormous computer, with high TL programming (for low AI). Even then you are stuck with a level 0 character, who gains XP like they are brain-damaged.
Anything less then an AI is just a machine. Not exactly what I would call a slave race, sure they might be relatively helpful, but not near as useful as another competent person. A voice controlled toaster is a gimic, rather then a citizen.
So, until you start looking at TL17+ there really isn't anything matching human ability, and there certainly isn't anything even able to stretch to being called an android. The cloest you can get is a human mimic, that if well programmed could be able to pass as human for *ahem* state events.
There are still places where a machine intelligence could be useful. For autonomous logic you have the advantage that loyalty can generally be assured if no-one has access to re-program the machine after initial programming. While the system that the intelligence inhabits has to be large, it is only large on a human scale, compared to starships and buildings they are relatively small. Automated factories, starship systems (such as Zen/Slave from Blakes7 and Holly from Red Dwarf), even systems as simple as those controlling telephony and communication could have extremely intelligent (for a machine) and capable systems.
On the military front using robotic spacefighters, grav tanks and robotic battlepods has certain advantages, especially if they could be remote controlled as well. This would allow you to use the superior human abilities when available, while still being capable of completing simple missions when communication is down or to go on suicide missions without effective loss of expertise.
So robots walking arround and being just more people is certainly unlikely.
However truly stupid robots also have their place. A partially robotocised infantry force, with many human NCO's and simple humanoid robots able to mimic and follow simple commands is a definite possibility, and quite useful if they could share equipment. Larger robots (ED209:Robocop) could be somewhat more independant, and have duties where eternal vigilance and no bladder would come in handy (simple patrols, guard stations).
Where there are a lot of people arround robots should be rare. People are quite cheap, and get all uppity (read riot) if a lot of them are unemployed. In industries where humans can break easily such as smelting and mining there may also be a large ammount of automation, though if the labor is cheap enough sentients would still be used.
The one big advatage that machine intelligences have is recall. A dumb lawyer who can cite ALL precendents would probably be better then a smart lawyer out of their normal juristiction. A corporate voicemail system able to remember everything, and be the entire corporations personal secretary.
IMTU there is both a robotic terrorist organisation (SELF- sentient engine liberation front - gratuitously stolen from UFO) and a large number of rogue high AI's, who tend to be very careful about upsetting the powers that be. There are also several AI run and controlled religions.
Enough rambling