I had read mixed reviews about Lewis Mountains' cabins and campsite, but I was very pleasantly surprised with what we found!
I was traveling with my parents and we arrived after hours (around 8.30 or so) on a Friday evening. The warden on duty in the camp shop (there's someone available 24 hours a day) was extremely welcoming and made sure we had everything we needed for the night. We stayed in cabin 10; it was clean, well furnished and more comfortable than other National Park accommodation I've stayed in. The warden was very apologetic about the "single" cabin (which contained a fully full-sized bed), and insisted on bringing a camp bed so that I didn't have to sleep on the floor--our usual set-up for 3-man trips!
We stayed for a couple of nights and I would certainly return again--what greater recommendation can there be!