Meh, its OK. Open rates for us was around 15% and that just didn't cut it. Switching to service that hooks right into our email/inbox and uses our esp to send the emails is significantly better. It really depends on the volume of emails you're sending per day. If you're sending more than 200 outbound messages per day I'd stick to active campaign. If you can get away with sending under 200 I'd look more into using an ESP that hooks into an automation platoform.
We use it for all our clients. Our favorite marketing automation tool. Plus their CRM is easy to use and fully customizable.
I use it for the drip campaigns for my clients. Its been 2 years and it works great for my needs. Their support is excellent as well. They’ve always gotten back to me within a few hours.