I'm currently carrying my Walther PPQ .40 cal. I alternate between concealed and open, depending on what I'm doing, where I am, etc. It's not the easiest thing to conceal, however.
As such, I'm expecting my Walther PPS .40 cal within the next few days. I'll still OC my PPQ or my XDm and will use the PPS for concealed. It will also make for a nice BUG when I'm OCing.