Gmail Add-ons
Sorry to be the one that has negative feelings about it.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.People need email service just because of the email function, nothing more than that.It's concept clearly has some limitations (attachment sizes, layout inconsistencies and so on) but it also doesn't have any deal-breaker problems.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.As a developer, I wouldn't risk investing in this feature.