Yeah strtod is still much slower (5x+ in many cases IIRC) than it needs to be. Rapidjson's is the best one I've found: http://rapidjson.org/strtod_8h_source.html
RapidJSON is an incredibly good library. Lots to be learned from there. My own implementation started off as a research project of my own, and only after completion did I research RapidJSON and SAJSON for inspiration. I seem to have takent he same path RapidJSON did in my library, which is working really well for me and allows for a very powerful set of optimizations in mutations primarily. Although I didn't think my design through as well as a library as RapidJSON, for anyone trying to pursue the same path I'd totally tell them to look into their direction.