I've used it and still do use it and have found it to be far and away the best of its kind. Your license is unfortunately limited to one domain and costs $195. You set it up on your own domain and it has every feature you could ever want in an autoresponder. The script install is relatively easy if you follow the instructions. There's a cracked version out there for those looking to save some money... hehe

Overall I'd give ARP a 10/10 and highly recommend it.