Well, maybe you could let your users answer that one for you by putting an SDK page up with 'coming soon - email us for a beta test' and tracking hits/emails. You'll probably change so much after launch that you don't want to be stuck trying to support API 1.0 so unless you get a lot of requests for it , it's probably a bad idea.

Thank you very much. You are right. There might be lot of changes after launch and thats when we will find out what users want us to deliver.

It shouldn't be a priority for your first version. Get it out there so people know what you can do first.

I agree with the others that you shouldn't focus on an API for rev 1.0 in order to get the product to market. But I would be careful and architect the code such that it can support an API...otherwise it's going to be a real pain in the rear to retrofit.

Depends on your target audience. What do your users want? If you don't know, ask them -- not us! (And if you don't have any idea who your target users are, you have a bigger problem than the API...)