essjay, I've been using one for a couple of years and can't recommend it highly enough.
If you are using it as a virtual card for online purchases etc, you don't need a physical card. I opted for the physical card at a fiver as I use it more than for online stuff.
Last year I was going to Thailand and bought £200 worth of their money from my bank to get me started. I got 8000 Thai Bhat for my £201. I went straight home and used the exchange feature on the Revolut app to see what I would get for £201 and it was giving me 8800 Bhat, a full 10% more.
I have used the card in Europe, USA, Thailand and Vietnam without any percentage being charged for an exchange fee. The rates are definitely the international rates being charged at that second....... you can watch them changing on the app every few seconds. I also have 2 FairFX cards, one in Euro and one in dollars.... their exchange rates are much lower than Revolut. (But they exchange pounds to dollars or Euro and ring fence them until you spend them)
As for international online purchases, I've bought from USA online at the banks trading rate at that time. A couple of times I've used it for bank transfers in Euro, without getting hit with the fee my bank wanted for an international transfer.
Where do they make their money? You can only withdraw £200 worth of cash from an ATM each calendar month before they charge you the minimal fee which I believe is 2%...... that's still cheaper than anywhere else because of them giving the international banking rate at that moment.
Some other great features..... my travelling buddy didn't receive his physical card in time for our big trip last year, but he did have the app and a virtual card. I paid for EVERYTHING on a three week bike trip, but as soon as I paid for stuff, I hit the "split the bill" option and he got a message asking if he agreed. One click later and his card loaded his share of the bill back to mine.
I know that was long winded, but I have no complaints at all about it. You can enable or disable security features like location, contactless or magnetic stripe.