Aww! Look how cute the little Data Kitten is!
Quandary may look innocuous but for just a single credit you get to send the Runner scrambling for their Yog.0 or Gordian Blade and investing far more money in getting past.
Many decks were playing a set of Enigma as basically their only Code Gates and to most intents and purposes Quandary is an improvement. There are some situations where the lower Strength of Quandary is a definite downside (Parasite, Atman) but in most circumstances Quandary will give you 95% of the value you get from Enigma at just 33% of the cost and, unlike Paper Wall, if the runner's Icebreaker ever gets trashed the Quandary will switch back 'On' and return to blocking runs.
I expect to see Quandary cropping up in quite a few Corp decks, particularly the rush versions.