The main floor bathroom, which was the only bathroom until we converted an upstairs closet into an ensuite, has lo-o-o-vely grey plastic tiles - simulated marble actually - on the walls and around the bathtub. When Michael ripped off those around the tub so that we could install a newly-purchased tubwall kit, he found that the plaster behind was mouldy and rotting. It wasn't a pretty sight and it didn't smell great either.
Fortunately, after 24 hours the area had dried out and the smell had faded. With the wall repaired, the first piece of the new kit went on easily.
Then, of course, we found the walls weren't true, so the rigid corners of the kit didn't fit quite as well as we would have liked. However, with the aid of silicone sealer, a renovator's best friend, it ended up looking pretty good.
Eventually we may upgrade to ceramic tiles in this area.
Then again, maybe not.