I used Interfolio and it was great; it really helps make applying much easier. Several medical schools will even accept your LORs electronically, which means that you submit them from your Interfolio account, and bam, your file at these schools is instantaneously complete. (My state schools all do this. 👍 ) If you are applying somewhere that won't accept electronic LORs, you can send them snail mail via Interfolio as well. To make a long story short, I highly recommend that you use it, especially because as a non-trad you probably don't have access to a pre-med committee letter.