Great concept and great execution!
I love the design choices here - all of them are solid. Requiring five-letter words makes it a lot harder than a hypothetical four-letter version of this game, so I had to think ahead and plan. Planning was made easier because instead of normal Solitaire rules where the covered cards are hidden, they're all laid out for you. I gotta say, I'm impressed with how much emergent microstrategy this super simple game has - I realized that I should try to empty the large columns early to retain more choices in the endgame. I planned around the K, the CC, and the A-heavy endgame. I thought long and hard before using my valuable S's.
And it was definitely worth it for the "reward" - I love touches like that at the end of a game. You didn't have to, but you did, and I appreciated it.