Actually there are a couple implications to using DAC that a person may want to consider.
When logging in via DAC, any login trigger you might be using to audit or otherwise control access will be bypassed.
If you have auditing turned on and are using the 'Fail operation on audit failure' feature the DAC may be your only way to get in if your attempt to connect is being rejected due to an audit problem.
These are both reasons to turn it on and reasons to leave it off depending on your situation. If a login trigger fails the login will be denied, even to SA, but since the trigger is bypassed on the DAC you can still get in to fix it. The same goes for problems with server level auditing.
You might have other auditing around use of RDP to access your servers and therefore use of DAC can be indirectly monitored with those controls whereas, if remote DAC is allowed, anyone who relies solely on a login trigger will not see the login. Anyone who relies on instance auditing will always see the login unless there is a problem logging the attempt. Via the DAC the attempt will succeed even if it might otherwise fail using a normal connection.
If your server is so pegged that you can't RDP but remote DAC is enabled, since the DAC has a dedicated thread you can always get in if remote DAC is enabled.