I just migrated all of my invoicing to Invoiless this past weekend, and everything just works as it should.
Branding my invoice was super easy, and they provided easy to follow directions to integrate my email and website.

Features I like:
-Automatic email reminders.
-Invoice scheduling.
-Ability to add CCs so you can email to multiple people at a company.

Thanks Invoiless. Great work on the app.