In 11 years and many many flying hours, I have never been in a situation where the autopilot is unable to maintain an acceptable flight path. If you have then I put it to you that you were somewhere you should not have been thus opening further questions.
I cannot believe that in 11 years of flying you have not been in a situation where it would be better to disconnect rather than trying to let the autopilot "cope" with the situation. Do we not fly the same equipment?
I don't claim to be an excellent pilot, nor will I ever disconnect AP, AT on an approach (whether its IMC or VMC) without the approval of the PNF. As many have already mentioned there is a time and a place to do this. I'm no idiot.
Bottom line is though that flying an ILS is a pretty basic flying skill.
I would be terribly ashamed if I would not be able to do this.