Take special note about point number 6
http://enticingthelight.wordpress.com/2009/02/04/15-truths-about-photography/
Actually, just take note of all.
Since you mention you are a newbie, I have a hard time understanding how you have already come into the quick conclusion that the lens is faulty.
I just picked up SLR photography a couple of months ago myself, and was somewhat disappointed the raw equipment did not had me "instantly level up". But instead of stating I made the wrong decision of buying inferior equipment, I realise I have ahead of me
volumes of photography and lighting topics/techniques to study and learn before I acknowledge that I have used all the limits of the equipment I presently own. There are still plenty I have not even realised yet, let alone mastered.
This is one of reasons why I strictly refuse to buy L lenses at this stage; my skill is no where close to absolutely requiring that quality. My use of L lenses have only provided marginal improvements so far. So my course of action is
practice, not purchase.
It is not necessary to purchase a top-grade guitar to learn how to play chords. Just grab an entry-level model, and concentrate on learning techniques and increasing experience. And enjoy the moments of slowly improving in photo output.