Chris & Olga's place was well suited to our needs. Right in Casco Viejo, there are lots of restaurants, cafes, markets, etc. close by. The Guggenheim is about a 25 minute walk away, but it is a very pleasant walk along the river. Booking and check-in was easy, and communications were timely and clear. The apartment is comfortable and well-equipped.
The one thing to be aware of is that there are many bars, clubs, etc. in the block where the apartment is. We were there on a Saturday night and there was a lot of street noise until at least 430 am. We are usually bothered by street noise, but we had and used foam ear plugs and did not have trouble sleeping. We'd suggest having those as a precaution.