After yesterdays session on the pigeons I took my brand new SX3 apart to give it the once over/clean and found it to be of a quality comparable with my other guns, it's ok to have "heard" that something is of a lesser quality/status but the proof is in the pudding as they say.
As an ex aerospace quality manager I can assure you that the internal finish is of a standard you will not be unhappy with and the woodwork on mine is of a very high standard for the price, after all it's going out into the field not hanging on the wall to be admired by one and all.
The only complaint I have is that I never bought it sooner.
As for rust if you don't look after anything made of steel it will eventually rust, as the manuals state for all guns, after use clean, check, and wipe over prior to putting away then it will be ready for use next time you need it.