I'd like to purchase this title if it uses Origin, because I have an existing account. I would also buy the original Mass Effect on Origin, so I could start at the beginning and import my character from 1 to 2.
Amazon does not currently offer Mass Effect 1 download. I'd pass on the sequel if I can't import a character across games.
Edit: Actually, I'd prefer Steam over Origin, but I read a previous thread stating that Steam is not used.