One thing you should consider is the electrical plug that comes with the genuine hitch: Its a 13pin round plug that (In Aus) only BMW sell.
In Australia the regular type is either 7 pin flat or 7 pin round, and noone sells an adapter except- you guessed it - BMW - and typically that will set you back $280 (although that is Australian $, so that would probably equate to the price of a big mac in $USD... Ha Ha)
Cheers,
Mark