Huh, that's neat. The wireless hub adds about 3ms to ping times, given the same number of wired routers/switches involved. (Wireless is an extra, third stage for those tests.)
All pings are against an idle Mac backup server. Middle numbers are wired from a really old, like, 1995ish, Pentium Linux box; top is from a 2011 Macbook Pro where I started poking at it; slightly improved numbers in the bottom column are a redo from a location with better wifi signal strength. Better signal did help, but not as much as I expected.
Initial Wireless - 2011 MacBook Pro (Low Signal)
Wired connection from 1995 Pentium
Second Wireless - 2011 MacBook Pro (Improved Signal)