I can't prove that with numbers, but oh yes, we think the API is one of our key "success" points!

One, the API helped us a great deal in terms of features / suporting different plattforms. Have a look: http://mite.yo.lk/en/platform/ – this is only possible because of our API, we couldn't have done that by ourselves, with a tiny team.

Two, integrating 3rd party products helps to spread the word about your service, especially, when the customer base is a pretty different one.

Customer wise: a pretty decent part of our customers makes use of our API to integrate intranet tools and the like. And it's a plus to highlight that we don't lock the data of our customers in. But if they hadn't become customers if we didn't have an API? Not sure about that.

Hey Julias, you should join http://www.thesmallbusinessweb.com if you're looking to find a good group of people building the market through integrations. We'll be working on time tracking data standards later this year in fact.

P.S. You should integrate with FreshBooks. (Guess where I work :)

Great site to research for anyone doing a web startup btw. Plenty of great examples to be found in their directory.

Thanks for pointing us to the SBW, sunir. We did stumple upon it already, but will explore it further.

I guess that last question is pretty hard to answer, but from what you say I can tell there's a lot of value to your customers in the API, hence it looks likes it is worth it. Thank you for your reply and congratulations for your success, I hope you keep growing and being profitable!