I'm a Mac user and went to check out what Paddle offers users, so I went to http://www.paddle.com/. It wants me to immediately log in or sign up, something that I'm not particularly inclined to do as I have no idea what you're offering. If you want to create a credible alternative to the Mac App Store, you're going to want to make it really, really easy for prospective users to see what Paddle is, what's available to buy, and what the process is like for managing their software library, updates, etc. This should be your #1 priority, as the best way to convince app developers to use your service is to be able to say that you have lots of users.
Paddle initially started as a marketplace for all types of digital content, and we've slowly transitioned into this toolkit for developers, offering payments, trials etc...
What you see at Paddle.com is reminiscent of our consumer-facing marketplace days, and we're close to pushing out a new homepage (this week).
One thing we're not trying to be, is a marketplace in a similar fashion to the MAS, we're trying to be the technology layer that empowers developers to not need a marketplace, own their customer, and take back some of the control that they typically give up by relying so heavily on a marketplace.
I do completely agree with you that the current homepage being what it is, and what we actually do being located at https://www.paddle.com/sell is confusing for potential customers who might want to work with us.