5′ 10.5″ here, I ride a 17.5. I could ride a 19″, but the extra standover and relatively long top tube anyway led me to go for the smaller size, and I’m glad I did.
The paint isn’t as bad as on On Ones say, but it can chip. First ride on my 853 steel one and a rock flung from my front wheel chipped some paint off the downtube. Other than that all ok though.
As far as rust is concerned, well, I hate to break it to you but all non stainless steel rusts! If it’s unpainted/unretreated it will corrode sooner or later. I just sprayed some shotgun oil in all the frame holes on mine, and down the seat tube, and 2 years on no rust issues still. You could go as far as waxoyling it if you were that way inclined! Or just leave it, it wil take 10 years or more even untreated for the rust to become a problem…