The pictures don't do this place justice, it's an extremely lovely apartment and you have everything you need for a stay in Vienna! We've been travelling around Europe and this is by far the nicest place we've stayed. We didn't walk anywhere but the location is great to jump on the tram or metro and we just brought a 48 hour ticket which is reasonable. We didn't meet Martin but he was a great host who was there if we needed him and supplies everything he can to make sure you have a great time in Vienna.
The building is undergoing renovation at the minute so if you're there in the week and do like a lie in I would suggest bringing earplugs, but it wasn't too noisey and it shouldn't put you off booking this apartment.