I usually use it to "tune" the local offset only.
When I play a new map, I normally ignore the approach circles completely and just hit according to the music. After about 10s or 30 hits I look at the meter and see if the hits are early/late, then adjust the offset & restart map. Once I'm satisfied with the offset I normally don't look at it anymore unless I get some random 100s throughout the map. I normally tune the offset so that the majority of my hits (sliders excepted) are focused near the centre of the hit error meter.
That's just how I normally use it though, I'm interested to see what others do with it too.