Until we can get consistent answers on what the hell it is supposed to actually do - there is no "definitive" version.
In 3rd edition, it specifically gave you all the "Natural" abilities and "Natural" abilities were not actually listed in the monster description seperately from Extraordinary abilities. So there was great confusion asyou were not supposed to get any Extraordinary abilities that were not natural - and those weren't actually listed.
In 3.5 you get the natural weapons but don't get attacks for having more limbs (a direct contradiction). You lose all of your form-based abiltiies (that are not in any way listed anywhere). And you can't use any part of your new form that is seperated from the whole (such as poison), but poison is listed as an example special ability that you get.
3.5 Polymorph is so covered in contradictions that custserv has officially thrown up their hands in dismay claiming a complete inability to figure out what it is supposed to do.
The "definitive" Polymorph will happen in 4th edition when they write the Monster Listings with Polymorph in mind and split the abilities into five categories:
1> Natural Abilities: you lose these when you change form, you get these from the new form when you transform into a new form. Examples: Constrict, Darkvision.
2> Extraordinary Abilities: You keep all of these when you transform, you don't get any of these from the new form. Examples: Stonecunning, Sneak Attack.
3> Supernatural Abilities: You lose all of these when you transform into a new form. If you use a particularly powerful form changing effect (such as Shapechange) you can get these abilities from your new form. Examples: Breath Weapon, Gaze Attack.
4> Magical Abilities: You keep all of these when you transform, you don't get any of these from the new form. Examples: Turn Undead, Phoenix Explosions.
5> Spell-Like Abilities: You keep all of these when you transform, you don't get any of these from the new form. Examples: Efreeti Wishes, Demonic Summoning.
When that happens, we'll have a polymorph that makes sense. Until then the DM just has to wing it every time it is cast.
-Frank