If the upper arm and blade is powered up and down as well as the lower arm, it is probably a good saw. If the upper arm and end of the saw blade is pulled back up by a spring, the saw is a candidate for being a door stop. That was the final purpose of my spring return jig saw (won't even call it a scroll saw). When it was no god as a door stop, it went to metal salvage.
A DeWalt 788 is what I have and I've been quite pleased with it. I've re-built it 2 times now, replacing most of the bearings each time.
Delta now offers a similar saw to the 788, and I own a lot of old Delta tools, but refuse to buy from the new Delta Tool Company because of parts and warranty problems. They are trying, but are far from being a good company to do business with, in my opinion.
Excaliber has had it's own problems too. But recently, they are back selling a similar saw to the DeWalt, again. They had a very good saw, but I don't know how the latest versions are doing.
Then there is the RBI saw by Bushton. The more recent variable speed models are supposed to be quite good. Some people like them. I'm just not a fan of their saws.
Right now, if I was to buy a new scroll saw, it would likely be a Pegas saw, but they aren't cheap. If price is really important, I would consider DeWalt, or maybe the Delta, but only because it is made much like the DeWalt 788, and I know how to get better bearings cheaper than their parts suppliers offer. Jet offers a scroll saw now, as does Seyco, but they aren't budget priced saws either, and I have no personal experience with either of them.
Just avoid the saws with the spring return on the blade, and you will likely have a pretty good scroll saw.
If you want to hook up with the scroll saw experts, consider joining www.scrollsawvillage.com
. You will find me there too, but also most other serious scroll saw users of the World.