I have one and it is a decent sander. I got my JSG96 for free and it will always have a place in my shop.
If you are going to be using it for grinding or sanding metal make sure you buy the proper belts and discs. At the bottom of this post are the McMaster Carr part #'s for the pads and discs that I use.
One thing I did do, since I use it primarily for metal was to replace the bottom cover / plate of the dust collection area. The one that is on it from the factory is plastic and the hot sparks from the metal would melt into it and cake up. I used the factory one as a template and made one out of sheet metal, to reduce the risk of fire.
The cast iron table is nice and can be easily moved for use on the 9" disc or the 6"x48" belt. This is what I do as the small table on the belt sander was not practical for some of the larger pieces I was sanding/grinding.
If you are going to be doing a lot of metal work and want variable speed and reversing on the disc. I would recommend building your own disc grinder. I am working on collecting pieces for my disc grinder build. So far I have the motor and variable speed controller and plan on buying this magnetic changeable disc system.
http://www.nielsendesigndiscgrinder.com/
For the platen and mounting of the motor. I am looking at buying or building something similar to this. Beaumont Metal Works Adjustable Work Rest for Disk Grinder
http://www.beaumontmetalworks.com/shop/item.aspx?itemid=7
If I had to decide between spending the $700 + for the JSG96 or spending the money building my own metal working disc grinder. I would recommend building your own as I am planning on doing.
McMaster Carr p/n#
Here's the belt I use from in 80 grit;
4168A625
Here's the 9" self adhesive pad I use in 80 and 120 grit:
47125A691
https://www.mcmaster.com/#4168A625
