This is a great game.
Despite not having all of the content of the paid version, there is still much fun to be had. I have played for over an hour, and I made a video for it on my YouTube channel. It's a game that takes from many other games, and is a great RTS.
WARNING! THIS REVIEW MAY CONTAIN WHAT YOU BELIEVE TO BE SPOILERS! PROCEED WITH CAUTION, FELLOW DWARF!
You are the dwarf overseer, and you see what the dwarfs be doing. If they start doing something you don't like...
This game does require a legitimate strategy, and due to the system of caves that appear, you never know if something will make you the richest dwarf in existence, or doom you and your hall. A dangerous cave can be many blocks away from the town hall, and depending on the danger inside, you can have an entire minute to deal with the situation at your own pace before it becomes a worrying threat. Sometimes you will uncover enemies. This can be a troop of 2 spiders, to 3 orcs and to a powerful warlock. To truly tackle these requires you to use fighter dwarves, which are very powerful fighters (and good miners). They cost 100 gold each (which by the time you encounter enemies you will have enough of), and are instantly available to fight.
You can place a battle tower in an area that you have mined for 500 gold, and this is VITAL to beating powerful enemies such as the warlock, as you can have up to 8 enemies. Of course, in a five minute arcade play-through, you may not need this. But in a 60 minute play through, you definitely will.
My one complaint is that you can't zoom out enough to view the whole arena at once, and this can be annoying when you have a load of dwarfs doing there own thing on multiple ends of the map. This has lead to many deaths in my playthroughs.
Overall, I give this game a 9/10.
And to top it all off, this game has a cameo from the ultimate dwarf: Yogscast Simon! :D