How do I get Xcode 4 to NOT clear the log between runs?

In Xcode 3, the console only cleared when you specifically asked it to. This was nice to quickly compare log output between runs.

In Xcode 4, the log clears between every run, and I'm looking for the setting (if Apple deemed it worthy of existence) that will switch this 'feature' off.

I feel the same way you do about this. That's why I've filed a radar at bugreport.apple.com. Please reference "Problem id: 9153445" when you filed your radar as the this will increases the incident count and making it likelier Apple Xcode team will prioritize a fix.

Since bugreport.apple.com doesn't allow you to search and view another's radar, I've copied the radar I filed at Apple at http://openradar.appspot.com/radar?id=1144401.

Thanks for reminding me that this regression needs people to start filing radars.

You can always just use the Log Navigator (cmd+7). It shows a list of past logs.