Thanks Marc, indeed this is spot on.

It's hard to convince anyone to switch unless they're having difficulties with their current provider (I do think that is an ongoing problem for even the larger players, e.g. Sendgrid were getting heat recently: news.ycombinator.com/item?id=…)

An integration with Rails is something I am considering, but I don't want to maintain lots of integrations so I will be selective about which frameworks to target. There's also something to be said about reducing library dependencies for a lot of app developers.

Obviously buying into the market by e.g. offering 12 months free could help but I would prefer to choose customers that are looking for quality service, performance etc. over the cheapest deal.

Thanks for your last comment especially - looking for and finding the right niche, figuring out how/when those developers/companies make their email provider choice and then influencing that choice is going to be my main focus for the immediate future.