Hi noticing that some of the information could be incorrect depending on the PayPal services used.
The URL to use in PayPal for IPN is fine for the standard http://www.storename.com/paypal/standard/ipn/ but if you wanted to use something like
PayPal Website Payments Flow then you need to use something like http://www.storename.com/paypal/payflowpro/ipn/
And if you you are in the UK you would be using /paypaluk// rather than /paypal/
The place to look at the different options is
This will save a lot of people time and frustration by updating these methods for v1.7 and above