If you plan to buy it, you should grab it in the next few days, as they will soon raise the price:
http://forum.kerbalspaceprogram.com/...rease-in-price
I bought it in September, after playing with the demo for a while. Worth every cent - even when it becomes more expensive.
The available mods are great and the developer team are the Anti-UBI in terms of information policy.
I'm praying to the gods of Kerbal that .18 will come out this weekend, never anticipated a patch for a game so much as this one.

(
http://www.kerbalcomics.com)