Pretty solid in its current state, promising future, dev actually interacts with community and the game was a functional and playable product when released on Early Access, which already makes it more likely to not get abandoned than 99% of games on here.
That being said, if you want a more 'secure' project or a game that can be played for merits other than sandbox elements I'd wait a month or even several. There's a big update coming soonish to the 'main' gameplay mode, and a huge list of not-yet-implemented features at the current time.
Gameplay wise. It uses a very well fleshed out sandbox building tool to design ships either on the fly or in advance that can be made or spawned into the various game modes. Eventually should feature a rather lengthy campaign that looks like it'll basically be a set of scenarios and goals, simple but entertaining, a Multiplayer campaign mode ("world domination" style gameplay with resource zones and stuff), and single battles pitting ships against eachother within a resource budget.
-The building tools are amazing, actually including features like fill tools, mirroring both 'along a line' and between two blocks allowing both odd and even number symmetry. Saving and loading sub parts of vehicles (tad odd at this time), and a lot of other "Blatantly obvious" things that it's always annoying when sandbox games lack.
-The game appears to have a fleshed out backstory and lore that the vehicles of the factions and the story missions are being created to match, and will likely feature a content rich and interesting game world in the end.
-The aesthetics. The game's graphical style is quite nice, with wooden structures and vehicles appearing a tiny bit ramshackle but still sturdy, metal stuff solid and sleek in form but covered in weld lines and rivets, the avatars(player controlled characters) interesting and unique. All in all it reminds me of steampunk with a bit of a clunkier appearance that I think fits the general design of the game perfectly.
-The weapons, while satsifying and powerful, suffer from a bit of 'one best option' problems. For example cannons are best served as being stupidly long guns with obscene fire rates, without much reason to do things like a massive caliber slow firing gun as you could make it rapid fire for purely an additional resource cost. Meaning "Bigger is always better, faster firing is always better" with nearly no exceptions.
-The physics engine for vehicles is a decent blend of realism and gameplay/CPU intensity concessions. Don't expect an accurate naval warfare simulator or realistic aerodynamics but it's definitely solid.
-The combant. Sans current minor AI derpiness the combat is rather well done, with versatile weapon options for your vehicles, ammo and fuel management being things you need to take into account, and lots of information presented in nice visual and auditory manners that don't look out of place. (Shell tracers that indicate shell type, energy shields showing up in world, engines changing pitch by power drain, thrusters for fortresses and jets showing information about themselves by the color of their trails, etc)
-The AI is a little clunky at present, does ok navigating and fighting solo but tends to ram allies repeatedly, make a beeline for stationary structures or sky forts and get caught on those, and the 'orders' system is as of this update not terribly useful or fleshed out, and results in even more of the above. Unfortunately, this is also a key feature of the game, and will almost be required for success in campaign after the coming update, so hopefully it's put in a better state in the next few updates.
-Lacking in content, obviously, it's an Early Access game, but the core gameplay ideas are present and largely functional.
-Multiplayer is in early testing this version, don't buy it for that, yet.
-Current implementation of campaign mode maps is unwieldy and a little derpy in how it handles diplomacy, e.g. allies will 'capture' any territories you leave defended only by structures or empty, but you will still receive resources from your harvesting objects there. Next version this should change but we have limited info on that, so perhaps hold off if that bothers you.