Although the devs have released some solid updates since launch (better graphics options, steam cheevos, etc.), there is a lack of diversity in maps. Game play is similar to Killing Floor but with defensive structures you can build.
However, most of the maps have two main entry points to your base plus one underground/through buildings entrance in the back making the maps feel repetitive. If you have some friends who are interested there's a 4 pack available.
It's a nice diversion with friends but don't expect to spend more than 1-2 hours on it at a time because of frustrating technical shortcomings and boring maps.