The High Queen has close combat uses - not fantastic but good enough to take on most other Heroes and Lords not mounted on beasts. She is suitable for an army facing High Elves because she also has the always strikes first rule and has an initiative of 9 plus 5 poisoned attacks.
She is also reasonably well protected from missile file having a toughness of 5, regeneration and immunity to poison.
The Queen's most advantageous attributes relate to her qualities as an army general (she must be your general if you take her to the battle).
The queen's bowmen, light cav and chariot crew can all be upgraded to have poisonous shooting attacks for +2 pts per model.
Also, and this is the best bit ! She can always cast the Incantation of Righteous Smiting once per turn and it CANNOT be dispelled ! How cool is that ?!
That means she can choose a unit to fight twice (with no retaliatory hits) or fire twice (even the skull catapult) every turn !
Now this ability, if used well, really could be a battle winner.
The Queen is accompanied by a curse so that anyone who kills her may regret it later in the game. Anyone or unit involved in her death has a 50% chance of being cursed. Cursed models and units forever after (ie for the remainder of the battle) suffer have a 3.5/6 chance of suffering an automatic wound every single turn - OUCH !
She has a few other bits and pieces like the Venom staff which is a ranged fireball like weapon and has the additional benefit of preventing any unit suffering wounds from moving in their subsequent turn.
All in all, providing you don't try to use her for challenges and Lord killing, I thin she's well worth the 420 pts whe costs.
Source: master-of-pentagram.blogspot.com