If you're looking for a spaceship combat mmo with a splash of rpg elements including mining, ship and weapon building and upgrading without a huge learning curve then I highly recommend Pocket Starships. One of my most favourite features is that as well as playing on PC, you can play on the go with your android mobile, Iphone/Ipad or Kindle. This works quite well for me as I can mine for materials on my phone while on the go (work lunch etc) and produce nukes, high powered ammo and upgrades, which can then be used in pvp battles when I get home.
The combat in this game is very addictive. What may seem like basic steer, aim and fire at first becomes surprisingly tactical and not only tests your reflexes but your split second decision making ie. when or where to unleash your nuke, how long to wait before using a health pack or whether to switch to short range weapon can be the difference between winning or loosing a battle. Teamwork is a large part of pvp made interesting with different ship classes (fighters - strong weapon, weak shield; engineers - repair beams, weak weapon; tanks - bonus building/base damage, strong shields).
The game is free to play and I feel the premium content and currency has been done quite well. You can become a top ranked fully equipped player without paying a cent, though putting money in to the game allows you to reduce the amount of grinding to get upgrades etc. Personally I have put money in to the game but this was mostly to support the developers.
In terms of continuity I have put 300hrs in to the game (longer than any other game I have played by a considerable margin) and have max upgrades for four ships and there is still plenty of other ship classes I would like to try, not to mention the new capital ship class which is soon to be released. That being said, you could go the other direction and just stick to one ship and reach 'endgame' (constant pvp with minimal mining/nuke production) a lot quicker than I have. The choice is yours.
This wouldn't be a fair review without some criticism. The game at this current point (April 2014) is quite polished, however there are some minor bugs, mobile device performance issues and some balancing issues but I am confident these will be addressed in the upcoming update. Nothing to stop you jumping in now and having a great time with an awesome community of players. If you see me (BRX89 - team Varian, US server) flying around say hi.