Epic game, lots of fun if you like building games. For $24.95, even at full price this game is well worth the value. The developers have made good on many of their promises, though they may have set their own bar too high. As it stands, if this game never got another update I feel like a certainly got my moneys worth - much better than many AAA games that costs $49 or $59 on Steam. No Man's Sky will have a lot more stuff to do (a similar game on the horizon), but it will also be a $60 game. ;)
So a couple points about Planet Explorers:
Build Tools ROCK! Love how easy it is to just pull and drag out whole walls, columns, floors you name it. What might take a few days in a game like Minecraft to build you can get done in 1 day since the tools make building both faster and more fun. The barrier to entry in regards to building your first castle right from the start is almost none.
Exploration is pretty cool. You can walk around for hours discovering new stuff, new mobs, locating hard to find resources. If you like to just explore and see what the world has to offer, this is a good game to do it in.
Smooth Voxel epicness! No more Minecraft cube clone with this game.
Combat is OK. It could use a little more fine tuning obviously, but it is there, it works and plenty of weapons to craft to take down both standard enemies and bosses. Yep, it has bosses and they are HUGE and dangerous. ;)
Colonies and multiplayer. Multiplayer just makes it great - team with friends, load up a previously worked on world and work on building your empire together. I currently play this with two other friends and we always have fun.
Active developers. It is a small team so what you can expect for a game of this complexity? As I stated before, in it's current state, $24.95 is a steal for how many features are in this game. If it never got another update I would be fine. That being said, the developers, while sometimes a little slow, stay on top of the project and continue to work on stuff and make it better and bigger.
In conclusion, with the transition to Unity 5 an already great looking game just got even better looking. Don't expect lightening quick updates and constant patches every couple weeks or month - and honestly, this game doesn't need it. It is stable, it is fun and offers something differnt from all the cube based Minecraft clones out there.