I think they're excellent servants, the perfect replacements for SimBots, which were useless and annoying. Much for fun to play with and interesting too. Don't have to worry about em breaking down if a dog decides to pee on them.
Though I did need to tweak my game to stop PlumbBot dancers from showing up at bachelor and bachelorette parties, because that's not sexy. Almost as much of a turnoff as the Tragic Clown jumping out of cakes in the original Sims.