For an early access game this game is already really playable as the sandbox mode works just fine. See this game as EVE offline. You fly your own ship (which you can upgrade or just buy a bigger one) around a HUGE universe that has highway like wormholes and natural wormholes. You can also move around anywhere under your own power so just traveling on highways or through wormholes isn't a must. There are hints of fleets in thwere but haven't been able to start one, although you can already by extra ships and leave them in your garage.
Upgrades for your ships are plenty and the weapon systems include, lasers, plasma cannons, railguns, missiles, and much more which you can freely add to any supporting hardpoint on your ship (light for guns, heavy for ammo consuming launchers). All upgrades and repairs happen on the station and I've noticed you really need to shop around the stations to get the best stuff.
Yes, this game has crews as even your starting ship is more then the usual fighters you get in other games. There are 3 shipstations which you can hire crew for. The crew gives you boosts on weapons or ship systems like engines, shields and cloaks depending on their skills. Again every station/planet offers different crews with different skills.
Random missions are generated all the time wich includes simple "go there and shoot.." missions, scan anomalies and bringing around cargo and passengers. You can visit many many stations (and planets) to upgrade, repair, hire crew, trade and lots more. The universe is very much alive as you encounter friendly and non friendly ships all over the place. Some sectors and stations really don't like you and can form a real challange when fighting in those sectors (enemy reinforcemants and stations blasting you). Fighting is mouse controlled, aim and shoot your light weapons by clicking the right mouse button and fire your heavy ammo consuming weapons with X. Also you can give the command "Fire at will" which will basically unleash all weapons on all in range enemies (this can be very much fun to watch while you just fly around avoiding damage with guns blazing).
Trade is already present in the game but is still in it's first stages so you get very little info on prices except for a news scroller that is viewable on every planet and station.
Patches are rolling out in a steady pace and the devs are very active on the forums (Post a question, suggestion or comment and you'll likely get a reply within the hour). This just gives you extra confidence to buy this game in early access and help in it's development.
Current Verdict July 18 2014:
Highly recommended early access game that is only getting better with each update.
*My above opinion still hasen't changed, latest update is again full of content. Recommend to pick up on current sale :)
Current Verdict September 16 2014:
Latest patches have added full controller support for fans of those things. Also the game is nearly complete as release is almost here, they've been busy with optimizing the game and adding final features, complete campaign/story mode is not finished yet but devs have indicated it's coming soon! (And in the past they've proven time and time again that they uphold their word!).
So still a big fat recommend from me at this final stage of early access.