I used Experiture for just over a year and they were so-so, not slick and sexy like some other UIs. They're also not as cheap as some of the big guys like Constant Contact or SendGrid. Deliverability became an issue for us so we had to find a new service.
Brevo - Innovative online Email Marketing solution to manage your contacts, create & send your newsletters and track your results. More than 80 000 clients. Best prices and attractive features.
eTrigue - Real-time Sales Acceleration & Marketing Automation Solution