We ended up here by accident. We tried to go to a different park, but it was first come/first served and it was full.  We were headed home along the highway and decided to try Memaloose. To our surprise, there were plenty of open sites, so we decided to give it a shot. We couldn't tell what had power and what didn't in the dark, so we ended up in an interior site that ended up being pretty nice.  We were under a few big trees, so it provided shade and felt kind of like we were in a cave when we were sitting by the fire.  

A few things to note - 1) The hookup sites are only on the outside of the B loop. 2) It's close to the highway and there is a train that goes by, so there is some noise, but it's not bad. 3) Most of the fire pits are really tall/deep. It's not ideal for roasting marshmallows.

Overall, it's a good park.  Some sites have great views of the river, and it's very central to exploring lots of stuff in the eastern Gorge area.