I'm wondering if there has been any research done on the health issues (if any) on drinking from stainless steel coffee cups. Links or sources please. I couldn't find any. I've stopped drinking out of the plastic ones because I'm concerned about possible leaching, but I'd rather not jump from the frying pan into the fire.

The whole concept of "stainless" means that the steel is made to resist rusting, which is just another form of a chemical reaction. This would also help prevent the acids in coffee from attacking the steel and leaching off the metals in it. Notice I said "help" prevent. Acids attack metals, by nature.

Stainless steel does contain nickel, which is toxic. Switch to non-leaded, glazed ceramic mugs.