> I'm just not sure if managing the payment network, licensing and distribution support is going to be even more of a headache.
From my own experience (I have a few apps on the MAS + outside of it) something like Devmate+Fastrpring or Paddle makes licensing and payment processing pretty painless. Of course there's other issues like what happens when Paddle or Devmate go belly up ande stop processing license activations. But still it takes only a weekend to get it to work and once you get it to run it just works.
The real problem though is that the Mac software ecosystem outside the MAS is dead. No user goes to those huge software directory websites anymore (my traffic from MacUpdate & co. is almost zero). (Funnily enough before the MAS went live Apple had a list of OS X software. It was a great source of high quality traffic back then. But it wen't offline with the introduction of the MAS).
The only way to get your app infront of users is via SEO (which means that you take your eggs from the MAS basket and put them all into the Google basket) or by spending loads of money on PPC ads which won't give you a positive ROI because $39 is now considered hugely expensive for software.
Social media, blog posts, etc. are all nice in theory but won't convert to paying users. You made a funny cat picture that went viral and sends thousands of reddit users to your website? Great, but no one will download your app. They just want the cat picture.
The same goes for paying $10k for a blog post over at daringfireball. People will visit your website but won't download.
Buying ads directly on blogs, forums or twitter/facebook? No one cares for those. You will just lose money.
Marketing your own software got really hard nowadays and if you're not one of the "famous" developers removing your app from the Mac App Store just means that you will lose most of your revenue.
Great for Sketch that they can pull it off. But most devs can't. Which makes Apple's negligence of the MAS even worse.