Sounds interesting...but as a guy, I'd probably develop feelings...also, it feels like being used...but then again, you're the one getting some. I think it's okay. For like people who aren't good holding relationships and the like. But, I don't know. Each to their own.
Works for some people, and doesn't work for others. Most of people may get emotionally attached and hence may not work for them. I had one experience in my life when I was 22 (I'm now 30) with a girl whom our relationship was merely FWB. It seemed like an AMAZING idea at the moment, but then, and because I had no single feeling for her, I felt disgusted (of her in fact not of the idea), but however I prefer sex with mutual feelings.
I have a friend with benefits right now. We recently began to develop feelings for each other, but we don't want to be in a relationship because once you get into a relationship, you're kind of trapped. Right now we're together because we want to be, not because we're obligated by having the label of "boyfriend" and "girlfriend".