The ease of updating Ember apps is really great. I've helped take apps through the early 2.x to latest 3.x. There has been some tedious work involved, but on the whole, I usually know exactly what to do to get the new features. Not breaking existing features is a godsend, because the rest of the team can keep developing features and we can introduce new features via lint rules at a reasonable pace.
Speaking of newsletters, I'd like to voice my love of tinyletter.com. I used it for the first time in 2010 and it's just as awesome 5 years later after the Mailchimp acquisition. I just started another newsletter on it last week and love the experience of using it. (Not posting the newsletter here because I don't want more subscribers and it's off topic), but yes. TinyLetter is <3.
I'd be pretty likely to buy music off Twitter if it was released there exclusively. Come to think of it, I'd be highly likely to buy one-off items from Etsy, Gumroad, and Amazon through my Twitter stream as well.