We've got two M605s, relatively new to us; replaced two M604s that each seemed to have taken an electrical hit with different results. The M605s each included a GPS puck, but we also already had other corrected GPS sources, so only one puck is actually mounted in the boat and it's not actually connected to its radio; just there in case the other GPS source craps out. Seemed to work well enough when we tested with it, but I wasn't able to determine whether it accesses the WAAS correction signal or not...
We don't have the AIS option (already had it, separately) so can't comment on that.
Otherwise, we like the 605s well enough. I'm still learning the different menuing system, for faster switching between hailer and radio and so forth... but it's not difficult, just different from the 604s...
South River, Chesapeake Bay