What are expats' thoughts on purchasing an apartment in one of PP's luxury buildings for investment?

For the right price in the right area why not? It's the capital, it has all the facilities, and unless the KR turn up again and empty the place there should always be a rental market. Watch out for maintenance costs. Some people have said that prices are low at the moment because of oversupply, so maybe get a hard deal in and maximise your return.