I have used low fees without many problems, sometimes to my surprise the transaction gets confirmed within a short period, some others I've had to wait days for them to confirm. On a couple of occasions after waiting forever, the tx were discarded by the network and the bitcoin returned to my wallet.
Before, I'm setting my transactions at the lowest priority and fees today are really high. I did experience to wait for almost 20 hours before my transaction gets confirmed because the fee is only 0.0002
BTC. I have seen people paying .001-0.002
BTC just for their confirmation gets faster. Hoping this will fixed soon.