Thanks all! Regarding the shallower edge areas, I think it will be ok as is. This is where I plant sempervivums and some sedums that don't require much depth. Along the front and back edges you can see I placed 1 x 2" strips and along the short sides some rocks I scavenged from around the yard. I will remove all those in the spring; there should be enough roots established to keep the soil from washing away. I'm also looking forward to the wood taking on a more "seasoned" look over the next year or so.
I specifically shopped for some plants that would give good fall-into-winter color:
Blooming on the table now, Nov. 26: Erica darleyensis:
Photo taken a week or so ago, Calluna 'Warwick Flame':