Curious on this as well. My plan was to have a generic letter written that overviews why I chose medicine and my speciality and more generic PS stuff. My last paragraph I was going to alter for specific programs. Like I will keep the generic last paragraph about wanting a strong clinical environment, good teachers, etc. for the programs I don't have super high intentions of going to. for the programs I really want I will alter that last paragraph to explain my ties to their region, why I wanna go there, etc.
Curious on other people's opinions.