I'm still waiting as well. I sent my form in on September 1. I know this because I called Directv last night asking where my rebate was. The CSR said she saw a note on my account asking what my confirmation number was. This was the number you have to write on the rebate form itself. I did this on August 31 and I mailed the rebate in the next day.
Bottom line is after 15 minutes or so of the csr talking with her sup. they told me to wait another couple of weeks and if I hadn't gotten it by then to call them again.
This is strange because when I first signed with Directv they got the $100 DVR rebate to me in about two weeks. It was the fastest rebate I'd ever gotten.
I'm not concerned to much that Directv won't honor the rebate though. If all else fails I'll just call the number above.