They're pretty capable for a $1000 desktop printer. The next step up is about $10-250k ones which are used for industrial prototyping. I've messed with several iterations of the makerbot(http://www.makerbot.com/) and it just keeps getting better, it would be more than capable of building the body, fins, and nosecone for a rocket, you couldn't do the motor but you'd pretty much be able to print everything else you'd otherwise buy from estes. The original ones were build it yourself for like $900, I think the newest one is like $2k. The other option is called reprap which is in-line with the older makerbots and you build it yourself so you can choose which things you wish to upgrade or spend money on to customize it to your requirements.