It completely depends on how well they are cleaned, the amount of dogs that have been in them, the amount of soft furnishings they have and how responsible previous renters of the property have been re the rules on where dogs can and can't go.
We have family and friends that stop in pet friendly accomodation as they have dogs and generally don't have a problem. It tends to either be absolutely fine or it absolutely stinks.
Judging by previous threads on dog friendly accomodation, most people seem to ignore the no dogs on sofas/ beds/ upstairs rules.
We always make sure that the property is not pet friendly due to severe pet allergies.