I've just used it for the UK. I ignored the currency and just used exact numbers (so what I paid for my house in £ is the number I put into the site as $). Under taxes, I adjusted property tax until the dollar amount was roughly equivalent to my annual council tax, and adjusted the deductible to 0. Under closing costs, I included stamp duty as a buying cost. Insurance, maintenance, etc are all direct conversions.

Leaving most of the expected growth sliders in place, and taking into account that I've shortened my mortgage with additional payments, it estimated I'd only be better renting if I could get an equivalent property for about £565. In reality, the smaller house a few doors up rents for about £1500, and Zoopla estimates the rental value of my house at £1600. So, either I live in a really good buying area, or the US calculations don't translate well.