Played through the preview and really enjoyed it. My first impression was not very good, but the game grew on me (the homing grenades are fun!). It is a sweet, if very short experience (essentially one big level). The final game only has 6 more levels, so I hope they are much bigger compared to the one in the preview. It is very much a Duke Nukem 3D spiritual sequel and it shares a lot of the original's shortcomings and strong points: complex maps with plenty of secrets, enemies with hitscan weapons (more gunplay than projectile dodging), city environments, humor, etc. I prefer the original, but it is still a decent effort, and plays very well.
Despite liking it, I wouldn't recommend the purchase yet, unless you want to support the developers. It is an early version, still missing many features, balancing (hard mode is too easy, uzi and baton are underpowered IMO) and optimization (it has a lot of surprising performance issues despite the ancient engine).