Hi Curt.
It might depend on what kind of machine you're looking for.
We don't have a problem with eBay per se, but there are two potential problems with buying there. First, the sellers all seem to describe the machines as mint, but they just don't have any way to test them, so you have to accept the machine as is. Our experience is that what to these sellers is "Mint" is what we tend to call "Beat To Death." Second, our experience with shipping machines has been dreadful. Nobody knows how to pack them. Even the people who give it a good honest try just don't know what it takes. Having the UPS store put it in an oversized cardboard box and filling it with packing peanuts is a recipe for disaster.
If you're looking for a pro-sumer machine like an Otari 5050B or a Technics 1500, I think you're better off with Craigslist. You can see the machine before forking over your dough, and you can put it in your car and drive it home yourself.
If you want a studio machine, at least you have geography on your side. There are probably more of them in the LA basin than anywhere else on earth. If you find one you like locally on eBay you can ask for an inspection before you commit to buy. They also show up on Craigslist. And you may know someone in the studio business --especially the studio maintenance business-- who knows of machines for sale.
Good hunting.