Vertical Response is my "go to" email marketing tool. When the team is still trying to figure out which tool to use for email marketing and/or complete marketing automation, I buy VR credits to use until they're done with the decision making process.
It is easy to use and has a great variety of templates & designs for those who have never sent an email blast before. Yet it is still great for those of us who've been doing direct marketing for years.
It forces you to check your work and to test the email before sending. This is great for those of us who are rushed yet still want everything to be perfect.
Things I love:
~ Their reporting tools
~ Their upload tools are smart (no more emailing to dupes or broken email addresses!)
~ Ability to send again later to non-responders
~ Ability to send at a specific date & time in the future
~ Ability to buy credits on the fly if you need more than you have
It even has a postcard feature in case your industry is still using paper.
It also has a new "event" feature I've not had much of a chance to use yet but it looks like it will be a good tool (it's only about a year old).
When I was using it regularly in 2013, the Salesforce integration didn't allow team members to share historical data about email campaigns individual members were sending. Each person could only see their own email stats. Hopefully this has changed since then.
Integrated (mostly) with Salesforce. You can use VR inside of SFDC and share email credits with your team, but you can't share history of individual emails sent (as of mid-2013).
No "per user" fee.
No long term obligation. Having commitment issues? Not sure if VR is the right tool to use for email marketing? Thinking of other tools? Use only what you need until you decide. There is no recurring fee. You pay for a fixed number of email credits and are not charged again until you ask for more.
Don't have a designer and/or HTML guru? No problem. They have design templates and allow you to build the HTML using a graphic editor.