Unfortunately they still allow smoking in the cabins & on the balconies. The residual smoke smell in the cabins is usually not a problem but from time to time can be if there were heavy smokers the previous cruise. The cabin can be given a through cleaning if it has to, including changing of drapes & shampooing carpets but this is not done unless it's requested although they do shampoo the carpets on a regular basis.
The balconies can present another problem entirely. If you have a few smokers nearby & the smoke blows in you direction there's not much you can do except to use the balcony when they're not smoking but it's hard to do especially if there are a few offenders. We've been on trips where I swore I'd never get another balcony & still others where the problem was only minor. It's a hit & miss game and until enough people complain & make Princess aware of their thoughts, they'll never make any improvements to correct the problems.