If so, have you updated to using HTTP 1.1 headers in the response back to PayPal? Along with the new HOST header? This is required by February 1 2013.

Any issues?

I'm having the following issues:

The "VERIFIED" final response back from PayPal takes minutes to come in after the header data for that response (it's supposed to come in instantly all at once).

PayPal will continually try to send me the same IPN messages. In other words it keeps repeating that IPN because it thinks it wasn't received/acknowledged.

On my IPN transaction list on PayPal's site, there's no response code listed while it's repeating. Successful IPNs all have a 200 code. This is especially odd because if PayPal is sending me the validation response, then it MUST have received my initial post-back. Arrrgh.