Thanks to everyone for standing up for me. Even if my letter may not be grammatically correct, it is only D*CK*W*D* who critize minor details of those who try to help. I personally sent a letter (as opposed to making a phone call) for several reasons:
1) It is more formal
2) Sealed the deal (or lack of a deal) - I have paper proof of my response to their offer
3) It is so much easier to decline via a letter than face-to-face or over the phone (at least for me).
Good luck with your job searching! And congratulations to those who found a job and now have the luxury of declining other offers.