All of our Domain Controllers were moved out of the "Domain Controllers" container. We would like to move them all back to the the default container, but are worried about the side-effects. I am looking for feedback - thanks.
My gut says you'll have few (if any) problems.
If you were around when they were moved out of their default container, what happened then - because the same will likely happen when you move them back.
The only thing I can think of is 3rd party applications looking for a specific computer object in a specific OU/Container in Active Directory (that's a pretty silly thing for software to do, but I wouldn't put it past some vendors. **sigh**)
Added: When you do move the computer objects back, check that the Domain Controllers OU has the Default Domain Controller GPO applied to it.
Be sure to check Group Policy mmc to see what if any GPO's are applied to them in their current OU versus the Domain Controllers OU.