And they just came out with a "super battery" a couple years ago, which works all my current 18 volt stuff. And yes, it is quite wonderful to use on the boat... no cord to drag around and no fear from shock. I just take the extra battery with me when doing a heavy job.

I have everything from a flashlight to a chainsaw on this system. (got a "kit" several years ago)

Sure, Ryobi is not Dewalt, but the stuff works well enough.