We'll have an interview with Mass Effect chief Casey Hudson for you soon, but we wanted to give you this interesting little tidbit from the interview. Hudson says, "We're pulling in probably over a thousand variables from Mass Effect 2 into Mass Effect 3 if you're importing your save game."
It's an impressive number to be sure, but keep in mind, they're not all reality-shifting choices. For example, Mass Effect 2 is slightly different depending on what advice you give to Rebekah Petrovsky regarding her baby (remember her?). So maybe not 1,000 earth-shattering variables.