From all the G-Shocks I know (by far not all of them…), this is currently my favorite one. I love the case shape (a modern classic by now, just like the 5600…), the “medium” size and the solar power function. The latter means that you will never have to open that watch and it will stay waterproof to 200 meters for it´s lifetime, in theory.
Mine refuses to give me problems. It is not radio-controlled, as the G-6900 is intended for those markets like Australia where no signal can be received. The display is clear and crisp and the buttons can be “muted”, an added bonus for me. Out of the half dozen or so that I wear on a regular basis, this is the watch I go for in the morning when I do not know if the day is going to be rough 😉