One thing I found unrealistic
As indicated in the series and in Dark Horizons, there was a cognizable threat that the overseers (or whomever owned the slaves) would come in search of their property. It was obvious that these guys had superior technology to us earthlings, and could easily destroy and/or enslave us if they ever found earth.
I would think if an alien slave ship crash-landed on earth under these circumstances, the first thing the earth would do is devote a significant amount of time and resources to building technology and weapons to try and catch up to the alien's level of technology -- at least to the extent that we have at least a chance of defending ourselves from the alien threat. I know a few episodes touched on secret government experiments with newcomer weapons, but I would have expected this to have bene done on a vast scale, with entire cities of nations devoting the majority of their time, money and natural resources to further developing this technology out of fear that the aliens will show up. While doing this would significantly diminish our current quality of life, I imagine it would still have population's full support -- just like the way people war rationed during WWII.
Otherwise I think the series realistically touched on the xenophobia and cultural clashes that would occur if aliens were stranded on earth.