I'm from the school that it's better to have and not need than to need and not have.

When updating our panel one of the few instruments that survived is a WWII-vintage 3 1/8" wet compass. They knew how to make them back then - ours is quite accurate and consistent. While I have a battery backed up EFIS with magnetometer, I find myself always cross-checking with the whiskey compass. I guess that fits well with the way my brain works as I have an EFIS and moving map GPS, flanked by round engine gauges and a compass. The "old" technology works well to reinforce the excellent situational awareness provided by the "new" technology.

In the real world who cares about magnetic heading? Track is the important thing. Donning the flameproof suit now......

OMG this has been hashed out on numerous posts over the years. In the US it is not required if you have another method of magnetic heading indication such as the EFIS. Do what you want though, regulation should not dictate your comfort level.

Nope
 

Magnetometer with the EFIS and two GPSs.

Yeah, nothing like making up new requirements and regulations. Shees.

No wet compass, primary EFIS and backup EFIS, and my DAR never even brought up the question.

Probably because he's not re-living the 1940s and actually understands technology.

Yes
 

As per FAR and here for EASA rules one compass stand-alone is needed.

Of course I've one, a wet one, next time a PAI will be my choice.

As DAR here in Italy I've to check that one is mounted during building or in the renewing act of a Permit to Fly.

Magnetic Compass
 

Word of advice to Canadian builders. If you mount a Vertical Power VP-X unit behind your instrument panel, make sure your magnetic compass is far away from it. During my first compass swing, I turned the compass adjustment screws to the end and still couldn't compensate for the error.

Installed a S.I.R. compass on the roll bar brace. It works perfectly. Extremely accurate.

ATC still cares quite a bit.

My iPhone is my backup compass.