Annoyance? F3 debug screen reports Block Lighting (BL) level at head level, not foot level, making it very difficult to impossible to test BL for a given block. If foot level is reported, can jump to test head blocks and mobs spawn at foot level. It used to report foot level in 1.7.5?
To recreate: place a glowstone, stand on it, press F3 and view BL value.