Surely, going into a big runway during daylight, good vis, relatively flat area, no slopes, etc etc, it's no problem. It's when it's pitch black below an overcast layer at night and you're going into a 800m runway with only edge lights and approach lights, no electronic glideslope, perhaps reduced visibility, tight circling, drifting snow across the runway etc etc... That's a whole other ballgame. Absolute no-go in case of malfunctioning VASI/PAPI/PLASI as far as I'm concerned.