If you seach whole threads you'll come up with a few hits. I actually learned about Pohick from another DC thread. we'll be in the area in May and I decided to reserve the cabin for a couple of nights. We've stayed in a cabin smaller than these, so I think we'll be fine.
I went back and forth before I booked--first I thought it was a great deal, for our dates it's only $55 a night, then I got a little nervous when I read some other boards about how awful DC traffic was going to be to get to the metro station. (We're going during the week) And that it would be a longer commute into DC than some areas. Then after I did some more hotel research and was coming up with rates over $350 in DC the budgeteer in me knew we should give it a try. (Especially when I finally found a lower cost hotel in Alexandria, around $125 a night, and then realized it would be the same metro station that we'd use if we'd stay in the cabin.) My brother kept telling me "I'd rather stay in the woods than in the hood!" LOL So, today I booked it and then used Priceline and got a 4* hotel in Georgetown for only $110 for the next night. (Again, good since this part of our stay is midweek--regular rate was $335) Then we move on to another location for an event at College Park.
I can come back after our trip and let you know how it went. Hopefully others who have stayed will chime in as well.