1. We know the UI needs work and have plans to improve it. We are very aware that webkeys are not user-friendly; they were always meant as a stopgap measure while we build better UI. Some things about mobile here: https://github.com/sandstorm-io/sandstorm/tree/master/roadma...
2. The amount of work an app port requires varies a lot depending on the type of app. Self-contained apps that don't talk to the outside world can often be ported in a few minutes. But, indeed, some apps need work to integrate with the appropriate Sandstorm APIs. We've been working to make this easier by, for example, setting up an HTTP proxy inside the app which can make communicating with external OAuth services mostly transparent, while still respecting the Sandstorm permission model. With better tools we think we can automate most things, we just haven't gotten there yet.
3. There are multiple Sandstorm apps which let you post e.g. blogs with no Sandstorm UI frame around it. We have some features in-progress which extend this to more apps. But note that part of the goal of Sandstorm is to generalize a lot of the UI such that apps don't have to repeatedly build the same things, like login, access control, notifications, etc. We need to hang that UI somewhere, hence the need for that frame. But we have ideas that will make it look a lot more like an integrated part of the app UI in the future.
4. We dogfood a lot. We write design docs in Etherpad, manage tasks in Wekan, etc. Our github, google groups, and IRC existed before Sandstorm was functional. The main reason we haven't switched over is because switching is costly and it seems like there are better things we could do with our time.