If all the posts from folks who have no idea what is going on were removed, it would be far a more constructive thread. As it is, I have to tune out about 30% of the posts.
The folks claiming that this is a perfectly reasonable change by Google and that "it will be sorted out by the developers" clearly don't understand the issue. The folks saying "I didn't have a problem" or "Works for me" don't understand the issue. Any power user or anyone who bought an SD card specifically because 11GB (16GB - 5GB for Android) is not enough storage is having their functionality hopelessly crippled by this unilateral change by Google, and there is nothing third party developers can do to mitigate it.
This change essentially kills all File Manager apps and will prevent developers from writing their own apps to write to common areas like Music, Photos, etc. Instead, Kit Kat is a huge step backwards to how iOS works -- where data is siloed inside of each app. On my iPad, I had video files that were siloed inside of 3 different apps (FileApp Pro, CineXPlayer, and the built-in Videos app). With this change in Kit Kat, I'm basically back in the same boat as I was under iOS. Each app I install on Android that plays with videos is going to have video data siloed and inaccessible from other video type apps.
What Google SHOULD have done is defined some common areas on the SD card that apps can write to, but when you try to overwrite or delete a file, it's throws a system-level prompt asking if you are sure. This change would help get SD cards organized into Photos, Videos, Work, Play, Documents, let's say a preset list of ~10 folders they can write to. Heck, it could be an app setting to choose which of these each app can write to. Then all video type apps could play together. It would allow users to define which folders are "pooled" between apps. At the same time, this would have accomplished the same goal of stopping bad actor apps. But no, Google took the wrecking ball approach and now SD cards are as crippled as iOS.
This is a misguided change just to to protect a few folks who aren't careful about what apps they install and are surprised when "ZOMG Amazing Free Flashlight App MUST DOWNLOAD NAO!" mysteriously pwns their SD card.