Are you buying or selling? They're not as popular as some machines but I haven't heard anything bad about them either. I've passed on a couple at thrift stores that were under $25. They're just not that interesting to me even though as far as I know they're decent machines. I like older machines. If you're selling you can try getting an idea of asking prices for similar machines in your area from Craig's List. Keep in mind those are merely asking-not selling- prices. Throw out any really high prices you see. Those are completely unrealistic.
Sorry this is so vague. Appraisals are nearly impossible long distance. Too many variables.
Rodney