1, I don't have any personal expirience with this but after talking to a pre-med friend who used Interfolio this is what I found out. The main question is- Are all the schools you are applying to going to accept letters forwarded by Interfolio? Why don't you send e-mails to the schools and ask them if they will accept it. If they say they will accept it then you don't have anything to worry about. My friend told me that price-wise and reputation-wise Interfolio is pretty good. I hope someone with personal experience posts here. Good luck!