I stayed in Martina's apartment in May and it was great. I loved the location, it was really only 5 minuted from the Old Town Market, the only place where it took us more time to get was the Castle, but it's no surprise, it's on the other side of the river. Overall, the place was perfect for a short stay, literally just a bed to sleep and a table to eat a quick breakfast. We had a bit of a problem with heating (at first it was freaking cold in the apartment) and Martina was on holiday so she couldn't help and asked us to inform her assistant and in case it was really cold she recommended using the hob from the kitchinette. I wasn't very satisfied with such a response (I don't like to sleep in cold while travelling). Luckily, her assistant came and solved the problem, so I'd say we should thank the assistant.
The apartment itself was more of a room with some extra shower/entrance space. There was a small entrance to leave our shoes and coats and a big enough room with two-single beds (extremely soft), plenty of blankets, towels etc., a small sofa and a coffee table (perfect to sif your coffee in the evening), a small table with chairs to eat some breakfast, and a sort of IKEA hanger/wardrobe/shelves (not too much space for clothes, we travelled light but if we had more things it would have been tricky to squeeze it all on the shelves). The kitchinette/shower room was very small, there was a shower, a sink, a hob, a fridge, a kettle and some pans, frying pan, toaster and some leftover tea, coffee, toothpicks and of course plates etc. We didn't need anything more to prepare breakfast, but I think that's all you could prepare there due to the lack of space. It was tricky because if you were taking a shower and someone wanted some tea, there wasn't enough space. However, for our stay which was a mere 4 days, it was good enough, especially considering the distance to all important places. I would recommend it for any short stay in Prague.