There's a lot of good ideas in power shell. I like how they broke up the log stream into separate streams by severity. It still seems arbitrary and insufficiently general though. Why severity and not some other criteria?

What if programs could define any number of output streams? By default they could all coalesce into the terminal but other programs could connect to each one separately if they needed. Like an audio mixer of sorts: by default you get the mixed audio but there are ways to access each individual voice if needed.