I just switched over to these folks recently and they made the transition very easy. The feedback loop from your mailers is good also. With a breakdown of the bad stuff (your bounces and opt-outs with the why) and the opens, not open, and click-throughs. You can start for free, and grow your business with their tools. They also offer several ways to add your contacts, and a lot of templates to choose from for real ease.
I haven't found anything that I disliked. In fact, the pop-ups in the lower right-hand corner have helped me when I am in a new place wondering hmm wait. It's a very intuitive problem-solving system in my opinion.
These guys are a worth a look, and they probably don't show up on your search immediately (they didn't on mine) but I am glad I kept looking for the right fit.
For me it allows me to email about 1,000 clients, from a secure, dependable platform. And I know that they can one click out, which is important to my list integrity.