Hey, 7 wishes is a good place to stay, very good price/value considering location. Which is great! Karlin is without a doubt the best area you can stay in Prague.
The rooms are very clean, however the description on AirBNB are not very accurate. Their "1 bedroom" apartment was infact a studio (the sleeping place was separated from kitchen with half a wall). It's a bit disappointing since it was my main criteria when choosing the place. The washing machines are located in the common space in the building, they don't accept credit cards and there is no coins change machine. So it will be tricky to find enough coins. The rest is just fine, 24 hours check-in, luggage place is free.
PS: It's apartment hotel more like AirBNB, so don't expect to meet host and get tips how to spend time and etc :)