The Raspberry Pi Model B seems to be well documented. There are lots of guides and trouble shooting hints.
The Model B+ does NOT seems to be well documented. (This is made even harder due to the unfortunate name, as you can't search for '+').
I can't find any description of the LEDs on the newer boards. I am intrigued by the actual voltage at which the Red LED fails to light.
It is not difficult for an Electrical Engineer to examine the B schematics and the Raspberry Pi B+ (Reduced Schematics) to work out what is going on, but the target Beginner and Educational users need more explicit data.
Is there an accessible guide to the B+ connections, LEDs etc that I have missed?