Now that I have hit 1,000 hours into playing this game, I have decided to update my review, as I only had 80.6 hours at the time of my original review back in 2015!

TL:DR:
Keen Software House has finally come around and massively improved this game's multiplayer to an enjoyable state, updates are fewer, but larger and more quality, and servers are actually worth investing in with all the performance updates.

Space Engineers has massively improved in all aspects since it was released.
Keen Software House has made multiplayer pretty much entirely stable at last, I rarely see rubber banding which was horrific a while back, now you can effortlessly fly along or run around in a ship while it's traveling at max speed, which to me is a big deal!
The developers also are still adding content which is great, I remember when they used to add an update once a week, which may seem great, but it posed a lot of problems for the modding community, as frequent updates to Space Engineers require frequent updates on the mods, and many mods would fall behind as well as the game being prone to more bugs.
Also, overall performance improvements have really shown, the game crashes rarely, almost never. I can finally build very large ships and have them battle with little to no performance impact, and planets don't kill your computer anymore.
I have finally found it reasonable to invest into a server for me and my friends to play on now that servers require very little maintenance.

CONS
- There is a lack of weaponry, yes I know I can just build some projectiles and use gravity to launch them, or use mods. but I feel like there could be more variety than just missile and gatling turrets for the vanilla game. For an example: laser cannons, planetary to space cannons, or beam cannons. I consider adding new weapons a reasonable change because it was announced that console gamers who get this game will be unable to mod this game, so the developers should compensate for that major loss.
- The construction mechanics still seem bland, the traditional welders and grinders start to become a pain with larger ship/station builds. Yes you can build larger welders and grinders onto ships for quicker construction, but for how easy it is to lose everything with a small mistake, or someone/something's attack, there definitely needs to be a more efficient method of construction/deconstruction. For me I use a mod called the Nanite Control Factory, and it seems so natural to the game, I no longer play this game without it. Problem is, referring back to the console release, there will be no mods available, so people are stuck using old school welders/grinders.
- Lack of NPCs! This is something I long for, is more NPC interaction. There are Cyberhounds (robot dogs) and Alien Spider Things (Giant Spiders that will pop out of nowhere and scare the crap out of you), but that's all! I don't count drones or the random cargo ships as NPCs for obvious reasons. There needs to be actual NPC astronauts, perhaps along the lines of what Medieval Engineers was aiming for, NPCs that you could give tasks, trade with, or fight. I love the idea of attacking an enemy station or ship, breaking in, and boom, there are enemy NPCs waiting in there for you, or visa versa. Breaking into an enemy ship/station now is so dull, there is absolutely no life signs at all, just some interior turrets. Plus, NPCs could address the above problem with the tedious construction, deconstruction, mining, etc.. Just have your NPC crew do it, just picturing the sight of a bunch of astronauts working hard and watching your blueprints come to life sounds amazing!

Overall, this game has in my mind, become a massive improvement compared to what it was a few years ago!

Now that I have hit 1,000 hours into playing this game, I have decided to update my review, as I only had 80.6 hours at the time of my original review back in 2015! TL:DR: Keen Software House has finally come around and massively improved this game's multiplayer to an enjoyable state, updates are fewer, but larger and more quality, and servers are actually worth investing in with all the performance updates. Space Engineers has massively improved in all aspects since it was released. Keen Software House has made multiplayer pretty much entirely stable at last, I rarely see rubber banding which was horrific a while back, now you can effortlessly fly along or run around in a ship while it's traveling at max speed, which to me is a big deal! The developers also are still adding content which is great, I remember when they used to add an update once a week, which may seem great, but it posed a lot of problems for the modding community, as frequent updates to Space Engineers require frequent updates on the mods, and many mods would fall behind as well as the game being prone to more bugs. Also, overall performance improvements have really shown, the game crashes rarely, almost never. I can finally build very large ships and have them battle with little to no performance impact, and planets don't kill your computer anymore. I have finally found it reasonable to invest into a server for me and my friends to play on now that servers require very little maintenance. CONS - There is a lack of weaponry, yes I know I can just build some projectiles and use gravity to launch them, or use mods. but I feel like there could be more variety than just missile and gatling turrets for the vanilla game. For an example: laser cannons, planetary to space cannons, or beam cannons. I consider adding new weapons a reasonable change because it was announced that console gamers who get this game will be unable to mod this game, so the developers should compensate for that major loss. - The construction mechanics still seem bland, the traditional welders and grinders start to become a pain with larger ship/station builds. Yes you can build larger welders and grinders onto ships for quicker construction, but for how easy it is to lose everything with a small mistake, or someone/something's attack, there definitely needs to be a more efficient method of construction/deconstruction. For me I use a mod called the Nanite Control Factory, and it seems so natural to the game, I no longer play this game without it. Problem is, referring back to the console release, there will be no mods available, so people are stuck using old school welders/grinders. - Lack of NPCs! This is something I long for, is more NPC interaction. There are Cyberhounds (robot dogs) and Alien Spider Things (Giant Spiders that will pop out of nowhere and scare the crap out of you), but that's all! I don't count drones or the random cargo ships as NPCs for obvious reasons. There needs to be actual NPC astronauts, perhaps along the lines of what Medieval Engineers was aiming for, NPCs that you could give tasks, trade with, or fight. I love the idea of attacking an enemy station or ship, breaking in, and boom, there are enemy NPCs waiting in there for you, or visa versa. Breaking into an enemy ship/station now is so dull, there is absolutely no life signs at all, just some interior turrets. Plus, NPCs could address the above problem with the tedious construction, deconstruction, mining, etc.. Just have your NPC crew do it, just picturing the sight of a bunch of astronauts working hard and watching your blueprints come to life sounds amazing! Overall, this game has in my mind, become a massive improvement compared to what it was a few years ago!