Recently, during the Steam summer sale, I purchased the game Kerbal Space Program (currently update 21). After playing it for a few weeks, I have mixed feelings. Kerbal Space Program can best be described as an open-box space center simulator complete with a rocket pad and an airstrip.
The game offers great open sandbox gameplay with free updates similar to Minecraft, except it has no real story except whatever you make of it. If you want to go to the "Mun," then go, but do not expect a return trip unless you really know what you're doing.

For the casual gamer, it can be a bit overwhelming even after the tutorials, which could use a bit more explanation. For example, the rocket building tutorial consists of pod + fuel + engine = rocket and fails to note that while you are building, there is a control for what happens at each stage.
While the game will try to order these the way it thinks is best, it can and often does mess it up, resulting in parts being detached and parachutes being deployed at the worst possible moment if you are not careful.

Just getting into orbit can be extremely frustrating if you A) have no prior experience with this game or B) have no prior knowledge of rocket science. An example of how difficult this game is can be found in the KSP WIKI page for basic orbiting math.
Yes, everyone. For those who want to play the vanilla game as seriously as possible, you will probably want to break out the old calculator and a physics book. While this may seem daunting, there are still a few ways around all that math.

One way you can do it is to take the Wiley Coyote approach. Go crazy, build some rockets, and enjoy the fireworks. After a while, you might start to feel what it takes to launch a real mission. Remember to use F5 to quicksave frequently, and be prepared to walk away and try again later.
Alternatively, you can install a mod called MechJeb. I am currently using MechJeb version 2.0.9. This Mod has stuff for everyone, including more advanced information and autopilots that can do everything from putting your rocket in a certain orbit to rendezvous with other targets and docking to a port.
MechJeb works great for the most part but has a few flaws. It can also be a bit wasteful with your resources if you are not careful. Additionally, many people feel that the use of MechJeb is similar to cheating, as many people have put hundreds of hours into the game to do some astounding things using only the vanilla base game.

In the end, this game keeps calling me back to it with the dream of putting a rover on the Mun and creating a space station to help launch even bigger missions. There are two things this game really needs:
- It needs a difficulty scale for those who do not want to spend 3 days trying to dock a ship with their space station only to end up with more space debris than successful missions!
- It also needs a long-term goal to shoot for.
Minecraft has its Ender Dragon, and this game needs its own dragon to defeat. One simple idea would be colonizing another distant but still life-supporting planet or sending Kerbals deep into space to stop or deflect a killer asteroid headed toward the planet.
It does not need to be big; it just needs something. For the paltry sum I spent while it was on sale, I can say I have gotten my money's worth out of it, but I simply do not have the time and patience to take this game as far as others.
In short, its only flaw is that it has a specific target audience: the kids who always dreamed of being astronauts when they grew up. If you fall into this category and are willing to sacrifice time with other games, then give it a try. For those still on the edge, the game goes on sale regularly. There used to be a game demo, but that is no longer available.
Here are the direct links for the 1.0 demo from the email: Windows, Mac OSX, Linux. Yes, Squad used Mediafire to host their demo.
