This card is amazingly good.  For starters, it's easy to make this card invincible.  Simply boost it's attack power by 500, which is incredibly easy to due via Gaia Power, Demon's Axe, Power of Magicians, or even Giant Growth, and there is no way that a monster in battle can phase him.  However, be warned, because when he's in attack position, damage will still be done to your life points if he is attacked by something larger.

 

The Retrained Elf Swordsman is also a great card due to the current Japanese environment.  There are very few monsters that players actually put in their decks that can kill him.  Cards like Critter, Saint Magican, and Blood Vors can't handle this guy.  It would be rare for your opponent to play a monster that can kill the Swordsman, and even then, there are easy steps around the matter.

 

Also, he's a great wall.  If your opponent has a large monster out, lay him in defense position.  He'll protect you as well as any other card, and he's more likely to live through it, too.  This will force your opponent to take care of him, and while they are trying to do that, you can be taking care of their large monster.  Because of his unique abilities, he's a great distraction.  Your opponent will have to change their mindset and strategies to defeat him, and this most likely will throw them off a little.

 

He's Level 4, he's versatile, and he's just plain cool.  If your opponent can't kill him, you can use him as fodder to play a Level 5 through 8 monster, or you can use him all alone to dominate the playing field.  Combined with the right traps, he can protect your Exodia deck and give your opponent something to deal with.

 

To top it all off, Retrained Elf Swordsman is simply well-made.  He's the right affinity, he's the right class, and he's the right size.  Giant Rat, Critter, and Black Forest Witch can all go get him.  A magic card from Struggle of Chaos, SC-28: Calling Reinforcements, can also retrieve him from your deck because he's a level-4 Warrior.  SC-30: Resilient Warrior can bring him back from the Graveyard should anything happen to him.  If you want this card, it will be there for you when you need it.

 

You probably already figured this out, but Retrained Elf Swordsman is spectacular.  Watch out for him! ^_^