Howdy,
What would be a big gap to close between Nimble and others would be allowing multiple emails to be used by one sequence. Where I could pick from the 3 email addresses I have and have Nimble rotate my sequence across those two or three emails that I've configured. Idea being to spread the volume over more than one account in a round robin format. It's a big differentiator with Apollo and one reason thus far I've been holding onto that account. Their UI is crap though - I'd much rather do this all via Nimble.