I have used
Fictiv a couple times for very high quality prints to be used as masters for resin casting. At the time they were cheaper than Shapeways, but it's been several years. Parts arrived in just a couple days from one of their network members in NYC. I would use them again if I needed something with higher precision than a current typical resin printer can do (at the time DLP/SLA printers were nowhere near as cheap or common as they are now).
That said, printing from a service isn't cheap, and takes comparatively a lot of time. You need to be confident in your 3D design work to rely heavily on a service, because it's too expensive and time consuming to iterate on a part. This can be especially difficult for mechanical and otherwise functional parts. If it's a miniature figure or other mostly visual piece then it kind of is what it is---what you see is what you get. But if the design needs to interact with other parts, fit various fixtures, etc., that can be tricky to get right the first time, let alone your design changing over time. Granted, in some ways it's easier with very high quality prints from a service because the tolerances are tighter than consumer printers, but it's still a challenge.
There are several very good home printers now that cost about what you'll pay for 2--6 prints from a service and are straightforward and quick to get up & running. Certainly within the wheelhouse of somebody with advanced rocketry experience.
I totally get it if you just don't want to deal with setting up, running, and maintaining a printer. The cost of using a service could be acceptable in return for that. Very high quality prints of the final design also make a lot of sense to get from a service. But the time involved to iterate on developing and refining a design through a print service would be a real showstopper for me personally.
