Getting off the train before your final destination isn't a problem, you just overpaid for your ticket. Getting off after your ticketed destination is when you run into confusion.

Just to clarify, there is JR Osaka station and JR Shin-Osaka station. The shinkansen stops at Shin-Osaka, but NOT Osaka station. In Kyoto, all JR trains stop at JR Kyoto station, so it isn't much of a problem. Just note which track you are supposed to go to.