Everyone's different, but when there are times you 'need' black areas (areas too far away even for ambient) or for whatever reason, then you're left with using more lights, because ambient will effect all the blocks.

Since my project is 'simple' I set the ambient to whatever looks best and create lights with the same numbers as that ambient.... then 1 remove ambient light again, and add lights with a very pretty large radius. But thats just me.

Jason