Relatively certain a shift over the course of a
week would kill pretty much every macroorganism on the planet. Ruddy thing's spinning too much, too fast, for that rapid of a deceleration and re-acceleration to not bugger everything right into the stratosphere,* possibly literally in some cases. Maybe over a course of a century or two it'd be survivable. Maybe not.
Nothing good, in any case.
E: If you're looking for some answers beyond the cataclysm,
this site has some interesting broad-stroke responses.
*It would be roughly equivalent to a semi-truck slamming into a solid wall and then getting rocket-punched back in the opposite direction. Almost nothing of the truck would survive. Also that period in which we lost a substantial amount of our magnetic shielding (when the spin reached a near stop) would be radioactive hell. Hope everyone's underground getting crushed by tectonic upheavals then :V