I currently have 0015 and I installed 0017. When I tried to compile a sketch I received the following Java exception:
java.io.IOException: Target platform: "null" not found/ Make sure that "build.target" in the preferences files points to a subdirectory of D:\arduino-0017\hardware\cores
I tried adding the build.target "property to the file but it didn't help.
When I renamed the file, 0017 created a new one and the compile was successful. I think new releases should automatically migrate properties (use, rename, ignore. delete etc) from old releases.
BTW I had to type in the exception message because there wasn't a way I found to copy the message.
Edit: In some more testing I also found that the 0015 does not seem to start when reading the preferences files generated by 0017. While I am not expecting forwards compatibility, there should be backwards compatibility and co-existence i.e. maintain things used by previous releases so they continue to work.
Moderator: Please move to "Bugs and Suggestions"