Indeed this question has been asked many times on the forum such as this
thread, should you be looking for more opinions....
For me I've tried many of the big names and to be blunt nothing compares to a self hosted solution which leverages a third party infrastructure to send out the emails such as Amazon SES, Mandrill etc... The cost is like x100 cheaper, you get a massive free quota like 10,000 emails a day for FREE!
For that I use sendy which is integrated to Amazon SES... Its real easy to setup and once you add DKIM settings, I have found that deliverability to be awesome! You can add as many campaigns/websites/autoresponders as you want and with a free quota at 10,000 per day you really are ready to rock and roll with email marketing big time!!! In addition if you know a little PHP coding you can do some real cool stuff such as segmenting your list amongst other things with very little effort....