all their advice seems to be "I should have waited" - mostly to sell, but lately to buy.
I would say this, the days of buying an apartment here and sitting on it for a few years and making a bundle are gone.
I personally think it is a long term investment, 20/30 years you are looking at now and only if you have a personal interest in Poland.
You have indicated a preference for Polish summers, so in that case I would suggest a student rental, near the universities with good transport services, the students usually leave during the summers, allowing you to stay.
Don't expect great returns as the market plods along. Although you'd have to think about how students would treat the place, try to get students in their final year, they are more serious and party less (hopefully).
One of the things that needs to change here in Poland (and all other ex-communist countries from what I can tell), is the state in which you buy a new property.
I am not sure if you are aware that newbuilds are unfinished, grey shells. That means, no paint on the walls or ceiling, no flooring, no Kitchen and depending on the development, no doors, nothing in the bathrooms, no lights, nothing...
You have to finish everything yourself or get a company to do it for you.
It still has not sunk in to the mass mentality here that if a developer buys 300 toilets and has them fitted, it is cheaper than the for the individual buyer.
I think this should change, even if it doesn't, it should ;)
As this obviously adds time and money to the apartment and is generally a pain in the rear.