The issue was that you had to publish and maintain separate versions of your app for WP8 and WP7 as soon as you wanted to use the new SDK, with no way to just s

The issue was that you had to publish and maintain separate versions of your app for WP8 and WP7 as soon as you wanted to use the new SDK, with no way to just specify API level or feature flags. This was enough for a not insignificant number of devs to drop out of the already small market and lower the already limited app supply even more.