I topped up my Revolut account a few days ago (just having a play with it - am still loyal to Mondo!) Topped up 10 GBP, USD and EUR - no fees on any of them, all very good.
The only thing was that for some reason, all three transactions are showing as ATM transactions. I presume this is because they’re classed as cash transactions, rather than purchases.
I recognize this one might be fairly difficult to fix correctly, but it does seem that it’d be good to avoid assuming that cash transactions are always for ATMs. Perhaps checking against a list of addresses for known ATMs (I think there is an official list somewhere)?