We used them once as the wind was blowing hard down 27 and the sun was setting, decided to wait for the sun to drop behind the horizon, gives you another 10 mins or so before last light, enough to do a circuit and land, activated the lights it was like Xmas :) landed with plenty of light to spare.
It's safer than landing into the sun or trying the cross runway which would've been a hairy crosswind..... Having the instructor with me also helped as I wouldn't want to cut it that fine normally.