Well I must say I'm torn on Kerbal Space Program. I've seen it being played in the past by a lot of people; I've watched rockets explode hilariously, I've seen spaceplanes just wobble into orbit, I've seen people forget parachutes, mis-time stages...and it was hilarious. I've vastly enjoyed spectating this game and watching people have impromptu LAN competitions about who can build the most outrageous rocket that still reaches orbit.
So I was a little bemused when I booted up the game and was presented with something...less. Its a game that's horribly inconsistent overall, with some truly awesome potential, but mediocre execution.
I'll start from the top - Kerbal Space Program is about you getting your Kerbals into Space. For Reasons. And, using the unofficial mottos of "Its not the destination that counts, but the journey" combined with "everyone loves big explosions", we see to the heart of what the Kerbal Space Program really is.
You can create your own space rockets from modular parts that snap together, as well as some free form bits like extra structuring and pipes. After that you take the ship outside and try and launch it. And after the quick burial of A.N. Other the Kerbal, you go back inside to tinker a bit more.
Unfortunately, this is where the problems start for me, and where I have to keep reminding mysel the the game is in Alpha. The controls for moving around the hanger are fairly horrifying, and the scroll wheel doesn't scroll in and out, which is something you do need to do. There are several important buttons that never get explained, even though there is a tutorial. Similarly, there is no indication of what might be a good idea or a bad one; although this is often the fun part to work out, I think it's more entertaining when you know it's a bad idea, and you do it anyway. And it works.
Once you finally get a ship into orbit, the game once again impresses. Your session in KSP is not just one ship and one set of Astronauts - you can leave things in orbit and dock with them later, as well as re-supply to make trips to the moon (*The Mun). Solar distances aren't quite correct I believe, but are large enough to be an obstacle to overcome with thought, and taking a trip to the Mun isn't something to attempt lightly.
I have been told that the rather crippling shortage of parts and details on how to play the game can be easily fixed with liberal application of Mods and Wiki's, respectively. And although I can't exactly condone a game that does this, it does appear to work, and when I go to bed at night it's not the crippling issues I remember, but that moment I decoupled my secondary engines while they were still burning and they nearly hit me as they roared past (That time I survived; others weren't so lucky). Or the time I had such a large rocket attached to my space plane I basically had to add another plane on top to act as a spoiler, to stop me spinning out on the runway.
If you're interested in the game, read the Wiki, and if you're happy to rely on Mods, This will certainly be worth your time. With the game still technically an Alpha however, it's hard to push much criticism on it when it makes for hilarious stories, but know what you're getting into. The game is available on Steam Early Access, and development is ongoing.