Pros:
* Multiple useful projectiles. Her Charge Shot and Super Missiles are some of the most powerful projectiles in the game, and her Homing missiles are extremely useful.
* Can missile-cancel
* Down Aerial is a powerful spike
* Down Smash is quick and powerful
* Back Aerial still a good finisher, and Down Tilt is an even better one
* Forward, Neutral, and Up Aerials and Up Smash are quick and have high priority
* Bomb Jumping gives great horizontal recovery
* Tether Recovery option with Grapple Beam
* She is very heavy. Combined with great recovery options and lack of a huge target for her weight, Samus is one of the hardest characters to KO.
* Grab has incredible range
* Jab is quick, has a large hitbox, even hitting behind Samus, and clanks with most moves.
* Aerial tether has incredible range, decent stun, and no landing lag. (A technique known as Grapple Canceling or Grapple Boxing)
* Charge shot from a perfect shield block has guaranteed damage.
* Lots of combo options.
* If the situation requires it, the player can transform into Zero Suit Samus by using her up & down taunts.
[edit] Cons:
* Quick, high priority moves have low knockback and damage
* Grab is slow if it misses
* Somewhat sluggish
* Large Target
* Powerful moves are on the slow side, making it hard for Samus to score quick kills
* Slow rolling
* Can be juggled in the air due to being floaty
* A forced change in play style if Final Smash is used.
* Taunting to change into Zero Suit Samus is relatively hard to pull off correctly.