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.
No lower fees your transaction. Your transaction will get deprioritized by the blockchain. But it depends on the traffic on the bitcoin network. The more unconfirmed transaction will make the chain will be slowly to validate the transaction. If the people are in the competition to pay more and more to get their transaction to be confirmed in short time and the big competition of the fees will make your transaction fees get deprioritized and it can back to your wallet because the mempool is forgetting your transaction.