Absolutely. I served in an AmeriCorps state program for 6 months and then did VISTA for a year. I applied for Peace Corps during the first few months of my VISTA service. Being a VISTA, I was at an income level where I was able to get my health screenings for free through our local university (huge help). I referenced both the state program and the VISTA program in my application and during my interview. I also believe that the VISTA program helped me prepare for the Peace Corps style of working- grass roots, community driven, very individual with little supervision.
I only had an associate's in general studies, and although I had three years of intense youth development work (through a summer camp and conservation corp) I am absolutely certain that it was my VISTA that tipped the scales in my favor, and that allowed me to be a successful PCV.
I constantly recommend VISTA to people considering PC, and I am surprised by how few people have actually heard about it.