DH's words - minus any expletives - Compared to the 66, 15 and the 201, the 101 is not easy to service. Everything seems to be in everything else's way, so you are taking off stuff you'd rather not have to, to get at something else.
The controller built into the machine adds complications - especially if it does not work. You also can not easily rewire it to get around the male/female pin electrical connection. The oil reservoir system is a poor way to get oil where it needs to go. Since Singer did not use much of this on any future machines, it's likely they thought so too.
We could not test this machine until we had it back in the cabinet. It runs at one speed - medium slow. No feathering at all no matter how far you push the lever. Have no idea if that is normal or not. DH is going to look at the controller at some point to see if there is anything he can do about that. We've run into a few pedals that had two speeds (you can tell because of the contact points) while most are more variable.
I'm very happy to have the machine, DH is very happy there is only one like this.