What's your budget for the printer and how big are you looking to print?
I like the idea of one, but probably don't have any sort of compelling use case to justify buying one. That's never stopped me from buying something to play with before though. As such, I don't really have any requirements, but spending many hundreds if not thousands of dollars for a "toy" to mostly collect dust probably isn't terribly prudent.
Are you looking for a stereolithography (SLA) style 3D printer like the units sold by FormLabs or the more-typical Fused Deposition Modeling (FDM). I do not have one but I've been interested in the FDM 3D printer from Ultimaker. Their products are a bit on the expensive side but they're high quality. A coworker of mine has recommended the Anet A8 Desktop 3D Printer given how inexpensive it is if you want to play with one without investing a lot of money.
Are you using them for prototyping, low volume/one off production or what?
Everything isn't best manufactured on a printer. There are good reasons that, oragsmistamped, cast and CNC killed parts are so commonly used.
Funny you bring up 3D printers. I'm not interested myself but was chatting with a couple of young lady gamers/cosplayers at work that are thinking of getting a 3D printer to create various 'fashion accessories' and the like.
This is why I'm torn between the printer and the mill. The printer is much more accessible and cheaper, but not everything should be made of plastic. Likely it will just be to allow me to rapid prototype before sending the model off to a company for manufacture in something more sturdy. It will also serve well to produce the molds for production in carbon fiber.
Though I suspect it will spend 90% of the time printing toys for the kid. She's really liking to use Medium to design things, and it would be fun to physically print them out. A good route to start teaching her Solidworks and a production workflow I think.