Great pros:
Location - excellent, very silent place, located just between the National Theatre and Charles Bridge and 10 mins by walk from Old Town Square, you can reach almost everything by walk.
The owner - communicates proactively, tries to forthcome when you have special wishes (early check-in or so) - nothing to complaint on.
The atmosphere - it's very old house and although there's a little of original/genuine stuff (there are HPL floors and most of the furniture is IKEA, so nothing luxurious), the overall feeling is very nice and comfortable. I pesonally like the original paintings on the walls (showing actually street views around the house).
Comfort - although it's an old house, the bedrooms are pretty spacious, the bathrooms are not tiny too, warm water flowing, heating working well, kitchen features clean and ok. And the very wide beds are enjoyable too.
Price - for that location and comfort excellent value for money I'd say
An just few little contras:
Suitability for kids - It's definitely not well suitable for families with small kids - the stairways are steep, uneven and the handrails are partly missing and partly unstable (but the onwer knows and will try to improve).
Headroom - there are spots with as low as 1.3m headroom... would you be taller, you might almost need to get on your knees to access your room - it's a part of the genuine old house atmosphere;-) agree, but should be shown on some pics to make you ready for the "adventure" and to have a choice wouldn't you like that (not our case).
We also had a little issue with the internet connection (restart of DSL modem resolved that - no action was needed from the owner) and with the coding of the TV (resolved remotely with the owner).
I can highly recommend!