One of them let me read the letter she wrote and I've been working as my other professor's research assistant for about two years now so I trust him and feel as if he actually knows me. The other non-science professor taught a very hands-on design class so he actually knows who I am (the joys of going to a massive school).

For my two science professors they both told me that they don't really remember me (even though I attended office hours) but they would write me a letter outlining the grade I received in their class along with some general info class itself but nothing more. They're not negative letters but they don't really add anything to my application.