GRP
I don't fly IMC, but I have used autopilots to quite an extent in VMC.
My first comment would be that they work fine, when they are working fine ... but sometimes need a little adjustment. One Cherokee used to fly a huge lazy orbit on HDG! This is okay in VMC, where you can see what is happening and correct, but what about IMC??
Also, you are going to have to adjust pitch and power manually.
The other issue is to consider how your autopilot works. Is it simply adding aileron in response to deviation from a HDG or NAV instrument. Do you know what would happen if you encounter turbulence? Would an oscillation develop that could cause secondary effects and threaten loss of control?
I don't know the ansawer to the second point, but I would suggest that anyone using an autopilot in IMC should be very much on top of hand flying/scanning.
Perhaps this is one to discuss with an instructor?