I've gotten to the point in my career mode where it's easy to build my own spaceplanes for sending crews to orbit and the 3.75 m rockets make it more efficient to launch multiple cargos at once, so my KSOs have gotten a little dusty in their hangars (still love them, though). But for me, the station parts are indispensable. Case and point: my Interplanetary Transfer Vehicle Navalla A little over 6.1 km/s deltaV with accommodations for 5 kerbals, destined for Duna. The only things missing now are the lander, science packages, and the crew.