Yeah, I think it is too. As technical people its not a big deal for us, but you should make it as easy as possible for people otherwise you'll lose the business to a potentially inferior competitor who makes it nice and easy
Since one of the target market is businesses, I would assume they have at least 1 guy to do that for them (enter S3 key and ID). They aren't going to be part of your market if they don't.
Is entering your S3 secret ID and key too cumbersome for most customers?