There are huge philosophical implications that were dismissed far too easily:
Shepard was given his 'life force' (for sake of a better term) back again by the Wraith - the process is now seen to be reversible. But Shepard was made well only as a result of the Wraith taking the lives of two Genii soldiers.
Is that moral?
How can the team be so okay with that?
In the strictest sense they wouldn't have been okay with sacrificing two people to save one, but as the two belonged to the enemy (in their terms) then it would have been a kill or be killed situation, and therefore would have been more acceptable than having them die, and Sheppard die as well.
How long before someone takes a pet Wraith prisoner in order to keep it as a (Picture of Dorian Grey) 'life force' top up?
Instead of wiping out the Wraith, everyone will want one for themselves. There can now never be any peace in the Pegasus Galaxy. No longer can there be a treaty where the Wraith stay on one side and humankind on the other. No longer will the retro-virus be an option. The secret of eternal youth is much too big a prize. That Wraith has signed the death warrant on all Wraith.
What he did by giving life back was even worse for his species than taking a life. Discuss?
The Wraith has to choose to give, rather than take life. This means that the idea of Wraith as pets is a moot point. You would have to spend years conditioning it, assuming it didn't kill you first, before you could use its life-giving abilities. Also, you would have to be willing to sacrifice others for your own gain - since this is generally unnacceptable in civilized places, it would be difficult to maintain unless you had a horrendously malicious evil streak, or a lot of enemies.
The secret of eternal youth comes at a high price, very much a Faustian deal if you ask me, and how many people would truly be willing to take the risk. It would be more dangerous than trying to tame a hungry lion whilst wearing a suit made of ham!
Could it be, perhaps that the Wraith had somehow developed a sense of honour that none of the others seem to have. Unfortunately it only lasted until the end of the episode. Leopard and spots, eh!
You could see the giving back of life-force a mile away though. And Kolya escaping again? The man has more lives than a cat!