It's still in Alpha at the moment. What we are playing right now is the absolute base of the game engine. The creator wants to build a fully-fledged game around this in which you runh your very own space program.
I've gotten to well over 1100km above the planet before getting bored and building another spacecraft. I was still travelling at over 2500m/s... :tongue:
I got to about 1000KM above Kerbin before I too got bored, I was going just under 6000m/s. All with stock parts (It was 1st stage 3 SRB's and then 2 stages of Liquid with 3 fuel tanks stacked).