Is it worth the price for a cheap spare or for soldering classes, or is it junk and not worth the trouble? (I already have a good Weller and Hakko, so this would just be a backup.)
Personally, I don't keep junk/cheap-o tools as spares anymore. I've found that they let you down. Keep an eye out for an older known-quality soldering station. My personal preference is Hexacon Select-o-Trac or Therm-o-Trac units. Partially because I have access to 80 LBS of tips, and partially because, inside, it's just a quad op amp and a switching transistor. I think I paid less than $20 for both of my Select-o-Trac irons, which came from eBay. I found one for Ian at the MIT Flea for around that price, too. I do keep a non-temperature-controlled, grounded tip Hexacon pencil iron in my toolkit though. Thanks, Jonathan