I have about 500 hours flying a Nimbus 3 in South Africa with a Bohli. They are very nice devices and very accurate - they give virtually none of the turning or acceleration errors that other mechanical compasses have. To use it correctly you have to be fairly prompt to adjust the banking knob based on what you are doing. I found that after about the first 25 hours it got relegated to being a secondary or tertiary instrument as there is much more to be busy with (both in the panel and outside) on an XC flight than the compass. And while I understood the concept of cloud climbing & flying with one I never had the guts to do it with the usually ballasted Nimbus. The one I used was already installed and the installation (which requires a lot of cutting and shaping on the top of the panel) appears to take a lot of work and talent to do neatly. Bottom line: probably not worth the time, effort & expense to install one - but if you had one in place you would not take it out.

Roy