I could never find anything actionable in NewRelic. Seems like interesting data, but nothing I could optimize for. Skylight has identified slow performing areas where we've worked on and watched a downward trend.
Come on, I love Skylight, but really! Slowest queries, slowest requests, breakdown of every hit into details how much time everything took. It gives you too much actionable data if you ask me. You can constantly optimize some slow-pokes, I have to remind myself to not optimize pages that are not most used.