I use GetResponse to carry out all my email marketing. I know people have their own software and scripts on their own servers, but I'll stick to a 3'rd party service that does all the background work to make sure the software is running correctly and I'll get a good delivery rate when I send out my emails.
For me it's just hands off and I don't have to worry about it ever. I know a lot of people like Aweber or Icontact, but Getresponse is just easier for me to use and it's affordable.
I don't think anyone can go wrong with any of the top services. It just comes down to personal preference and features that one has over the other.