Gmail Add-ons
Sorry to be the one that has negative feelings about it.<p>Email is one of those rare concepts that is really hard to change or enhance. I can easily see Google abandoning this feature in 5 years.<p>People need email service just because of the email function, nothing more than that.<p>It's concept clearly has some limitations (attachment sizes, layout inconsistencies and so on) but it also doesn't have any deal-breaker problems.<p>Introducing external services integration to email sounds like taking a huge risk. How people manage their invoices, to-do lists and other stuff is changing faster than ever. These add-ons will require active development all the time to keep themselves up-to-date.<p>As a developer, I wouldn't risk investing in this feature.