Same for me, Albeit it at 30fps (I haven't attempted to change the .ini) I'm about an hour or so into the story with a longer playtime from just driving about, I'm debating not playing any further though, since apparently along with optimisation their could be graphical improvements (rain affects etc) so I kind of want the best experience from it that I can, if that doesn't happen I can always continue to play as is without an issue.
Shame so many people are having problems, its an above average game imo.