I love it! It's not boring, imo. Sam sounds warm and friendly to me. It's an all-around "good guy" name. I picture a generous, capable, likable man. You didn't ask, but I think it would work well with Jasper.
I haven't read the other responses, but I imagine a lot of people don't like Sam as a standalone. I do. It meets my (completely subjective) criteria on whether a nickname-name works or not: It doesn't sound babyish or embarrassing, and it wouldn't make me pause to see it preceded by a professional title or on a business card.