As JustAMom pointed out, while LOA's are wonderful assurance of an appointment if all other conditions are met, do *not* be discouraged if one is not offered.
When my son was interviewing for his congressional nomination, he about freaked out when another applicant handed the receptionist a letter with USMA letterhead before he went in for his interview. Though s did not know the contents of the letter, the receptionist congratulated the recipient and asked for a copy for their records. S was just sure that meant this applicant would get the top nomination and that he personally would have no chance for a nomination from this source.
That incident really psyched him out! However, we learned soon enough that s had no reason to panic. There is room for both of them in the Class of 2012: s received the principle nomination with no LOA, but as long as the other applicant had the LOA, he could be given a slot lower on the nomination list and still be admitted. That said, I know our senators and congressmen meet together to keep from duplicating nominations as much as possible to give USMA more leeway in offering appointments (although not all states and districts do this).
S and the "LOA applicant" - a recruited athlete - are now both sweating it out together in CBT. So as s would now say, "it is all good, mom, it is all good!"
So keep the faith! If you get an LOA, congratulations! If not, it is *not* necessarily the end of the journey.
Best of Luck as you go through this application process.