I have a Featherweight and a Singer 99K, both with full attachments and manuals, and they both work beautifully! I follow all of the maintenance instructions to the letter, and only use Singer brand oil, etc. I think it's well worth the small investment of time and effort.
My current sewing machine issue is that I now have my grandmother's White treadle, which sat covered up with an old bedspread in my mother's basement for over 35 years. I know I'm telling my age, but it's the machine Grandma taught me to sew on when I was in grade school. Fortunately, the original manual was rolled up and stuck in a drawer, and with lots of time and patience I was able to get it flattened out and copied. The machine, of course, had not been oiled for at least 35 years, so over the course of two months I oiled it, and have been able to get the parts un-jammed and beginning to move again. It took repeated oilings, of course. I am hopeful that I can get it really working nicely again. (The bobbin is working beautifully now!) The next problem is getting needles that fit. The one in the machine is almost twice as long as the ones I can find for sale these days. However, there is a Singer shop in town that has parts for Singers of all ages, so I am hoping they can look at the needle I have and find something that will work. If all else fails, I will have to clean up and sharpen the needle I have.