If you're concerned that it's taking forever to receive Oath Letter, you should be!
Here's my experience,
My interview on 6/16/10 went without any problem, IO just told me to wait for my OL in the mail, two months later still no OL, so on Aug. 31st, i had an infopass appointment, IO just told me, its approved, just to wait for it in the mail...
So 90 days passed but still no OL, called the 1-800 customer service, i opened a service request on my case, 10 days later, got a mail from LA DO, "were still processing your case" or something like that.
Then, on Wednesday 11/3/10,(more than 120 days have passed since my interview) went to downtown LA again... inquired about my case, IO sent me upstairs to room 6024, waited like 2 hours...
Anyways, Officer just told me that my paperwork got mis-routed(misplaced) or something, that she is going to personally hand it to the person that schedules the Oath taking ceremony, "Sorry for the inconvenience" asked her when will i receive my letter, but she can't tell me...i was pissed but i just stayed cool =(
Anyways, checked my mailbox today, then bam! i finally got my OL after more than 4 months. =)
So my advice to those people that are waiting for their letter, check this thread for normal processing time in your respective DO's and compare.
If you feel like it's outside the processing time, schedule an infopass right away! chances are its just sitting on someone else's desk,
And don't take the " just wait for it in the mail" answer, it seems like they dont want to help you, until 120 days is over.
Just tell them what happened to me or something, good luck !
P.s.
Im taking my Oath on Nov 17th at Pomona Fairplex, see some of you guys there !