A lot of it depends on the viewfinder, as well as the particular scene you're trying to frame.
Smaller, crop-DSLR viewfinders, you might want more focus light. Huge FF pentaprisms, maybe not so much.
And in my case, Sony-A55 with electronic viewfinder, first generation, that 'helpfully' goes black with manual settings and a manually synced strobe (camera doesn't know strobe is there, and is trying to give you a preview of how lit it thinks the shot will be), I need a LOT of focus light or my view is sometimes nonexistant. (All later SLTs from Sony have the ability to disable this 'feature'.)