we have never been but we were told to get Lev's at the airport, then only change money up at the hotel or banks, do not change your money with strangers because it will probably be out of date currency
Also another ATM in the village, towards the Rila. I used them last year and got a great exchange rate, and didn't need to have loads of cash swilling around.
I have a work colleague who is Bulgarian and knows the resort very well, it is my first time this year (I'm flying out on the 23rd and praying for snow) , he recommended taking some Lev with you (£150) which you can get from the post office and then exchanging at the Gondola as that has better exchange rates than the hotels. his other recommendation was to buy currency using master card as the fee is approx 2% not the 12%+ if you use your debit card.
The bank at the gondola is shut now (I think!) but there is a Biochim Bank by the taxi rank opposite the gondola where I'd change my money (if I was changing a lot) otherwise, used debit card - there and at the Rila and got a very fair rate - take a small reserve in Levs and use ATMs.