I have, it seems pretty sporadic. Sometimes I'll wait a few days and PM again and I'll get a response saying they never got the first one. I try to reply on the thread and PM, just in case.
I suspect I'm running into the same problem; I sent a few PMs with no response, but in one case the recipient noted he didn't receive the PM. Odd, as I hadn't had a problem with PMs in the past.