Which email marketing module/add-on?

[johnbiggscr]

We are investigating e-mail marketing for our shopsite sites and are looking for feedback on what option other users decided to go with and what their thoughts are on pros and cons.

As far as we can see there are 3 obvious ones to choose from:
1) The email marketing module.
2) Constant Contact.
3) ez.newsletter targeted email marketing.

Has anyone used any of these and if so what are you thoughts, and are there any pitfalls we need to avoid?