this week's Wandering Monsters article that all golems are cited as being Large, but in the Bestiary the flesh golem only weighs in at Medium. I actually kind of like that, and think that golems should by default have multiple size categories so that we could have an army of Medium-sized clay golems (or crank them up to Huge).
Thankfully 3rd Edition Revised toned things down, so even if a fighter lacked a specific weapon the damage resistance only dragged things out instead of making it insurmountable (because, again, magic immunity). Rogues still got the short end of the stick, unless they took a feat that probably existed that let them critically hit Constructs. 4th Edition made things even easier by removing both damage and magic resistance, as well as allowing crits (so, yay for Sneak Attack).
So right away I do not like the pair of golems featured in the lastest playtest packet's Bestiary: they are both immune to nonmagical, non-adamantine weapons—though that might change, as the article mentions that it only resists non-magical weapons—and can only be affected by either spells with specific energy types or all of three spells. Well, at least we still have critical hits.
I think that at the least the designers could go with 3rd Edition's damage-resisting model, so if the party finds themselves without magical or adamantine weapons that they are not good and screwed. Personally I would just give them advantage on saves against most magic as opposed to outright immunity. Why are they even immune to virtually every spell in the first place? Why does this not crop up on more constructs?
I would also like to see golems get a lengthy list of optional/alternate traits to better represent wizards and clerics experimenting with them; why should iron golems be the only ones with breath weapons? For that matter, why do they all have breath weapons? Also, it could be cool to have the animating spirit escape and attack—or potentially reward the—characters.